keyprov P. Hoyer
Internet-Draft ActivIdentity
Intended status: Standards Track M. Pei
Expires: August 25, 2008 VeriSign
S. Machani
Diversinet
February 22, 2008
Portable Symmetric Key Container
draft-ietf-keyprov-portable-symmetric-key-container-03.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
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Abstract
This document specifies a symmetric key format for transport and
provisioning of symmetric keys (One Time Password (OTP) shared
secrets or symmetric cryptographic keys) to different types of strong
authentication devices. The standard token format enables
enterprises to deploy best-of-breed solutions combining components
from different vendors into the same infrastructure.
This work is a joint effort by the members of OATH (Initiative for
Open AuTHentication) to specify a format that can be freely
distributed to the technical community. The authors believe that a
common and shared specification will facilitate adoption of two-
factor authentication on the Internet by enabling interoperability
between commercial and open-source implementations.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions used in this document . . . . . . . . . . . . . . 5
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Offline Use Cases . . . . . . . . . . . . . . . . . . . . 6
3.1.1. Key migration by end-user . . . . . . . . . . . . . . 6
3.1.2. Bulk import of new keys . . . . . . . . . . . . . . . 6
3.1.3. Bulk migration of existing keys . . . . . . . . . . . 7
3.1.4. Key upload case . . . . . . . . . . . . . . . . . . . 7
3.2. Online Use Cases . . . . . . . . . . . . . . . . . . . . . 7
3.2.1. Online provisioning a key to end-user's
authentication token . . . . . . . . . . . . . . . . . 7
3.2.2. Server to server provisioning of keys . . . . . . . . 8
3.2.3. Online update of an existing authentication token
key . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Portable Key container definition . . . . . . . . . . . . . . 11
5.1. KeyContainer . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Device . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.1. DeviceId . . . . . . . . . . . . . . . . . . . . . . . 13
5.3. Key . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.3.1. Data (OPTIONAL) . . . . . . . . . . . . . . . . . . . 17
5.3.2. Usage (MANDATORY) . . . . . . . . . . . . . . . . . . 17
5.3.3. ValueFormat . . . . . . . . . . . . . . . . . . . . . 21
5.3.4. PINPolicy . . . . . . . . . . . . . . . . . . . . . . 22
6. Usage and profile of algorithms for the portable symmetric
key container . . . . . . . . . . . . . . . . . . . . . . . . 24
6.1. Usage of EncryptionKey to protect keys in transit . . . . 24
6.1.1. Protecting keys using a pre-shared key via
symmetric algorithms . . . . . . . . . . . . . . . . . 24
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6.1.2. Protecting keys using passphrase based encryption
keys . . . . . . . . . . . . . . . . . . . . . . . . . 25
6.2. Protecting keys using asymmetric algorithms . . . . . . . 27
6.3. Profile of Key Algorithm . . . . . . . . . . . . . . . . . 28
6.3.1. OTP Key Algorithm Identifiers . . . . . . . . . . . . 28
6.3.2. PIN key value compare algorithm identifier . . . . . . 28
7. Reserved data attribute names . . . . . . . . . . . . . . . . 30
8. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 31
9. Security Considerations . . . . . . . . . . . . . . . . . . . 35
9.1. Payload confidentiality . . . . . . . . . . . . . . . . . 35
9.2. Payload integrity . . . . . . . . . . . . . . . . . . . . 36
9.3. Payload authenticity . . . . . . . . . . . . . . . . . . . 36
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 37
11. Appendix A - Example Symmetric Key Containers . . . . . . . . 38
11.1. Symmetric Key Container with a single Non-Encrypted
HOTP Secret Key . . . . . . . . . . . . . . . . . . . . . 38
11.2. Symmetric Key Container with a single PIN protected
Non-Encrypted HOTP Secret Key . . . . . . . . . . . . . . 38
11.3. Symmetric Key Container with a single AES-256-CBC
Encrypted HOTP Secret Key . . . . . . . . . . . . . . . . 39
11.4. Symmetric Key Container with signature and a single
Password-based Encrypted HOTP Secret Key . . . . . . . . . 40
11.5. Symmetric Key Container with a single RSA 1.5
Encrypted HOTP Secret Key . . . . . . . . . . . . . . . . 42
12. Normative References . . . . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 46
Intellectual Property and Copyright Statements . . . . . . . . . . 47
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1. Introduction
With increasing use of symmetric key based authentication systems
such as systems based one time password (OTP) and challenge response
mechanisms, there is a need for vendor interoperability and a
standard format for importing, exporting or provisioning symmetric
keys from one system to another. Traditionally authentication server
vendors and service providers have used proprietary formats for
importing, exporting and provisioning these keys into their systems
making it hard to use tokens from vendor A with a server from vendor
B.
This Internet draft describes a standard format for serializing
symmetric keys such as OTP shared secrets for system import, export
or network/protocol transport. The goal is that the format will
facilitate dynamic provisioning and transfer of a symmetric keys such
as an OTP shared secret or an encryption key of different types. In
the case of OTP shared secrets, the format will facilitate dynamic
provisioning using an online provisioning protocol to different
flavors of embedded tokens or allow customers to import new or
existing tokens in batch or single instances into a compliant system.
This draft also specifies the key attributes required for computation
such as the initial event counter used in the HOTP algorithm [HOTP].
It is also applicable for other time-based or proprietary algorithms.
To provide an analogy, in public key environments the PKCS#12 format
[PKCS12] is commonly used for importing and exporting private keys
and certificates between systems. In the environments outlined in
this document where OTP keys may be transported directly down to
smartcards or devices with limited computing capabilities, a format
with small (size in bytes) and explicit shared secret configuration
attribute information is desirable, avoiding complexity of PKCS#12.
For example, one would have to use opaque data within PKCS#12 to
carry shared secret attributes used for OTP calculations, whereas a
more explicit attribute schema definition is better for
interoperability and efficiency.
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2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
In the text below, OTP refers to one time password.
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3. Use Cases
This section describes a comprehensive list of use cases that
inspired the development of this specification. These requirements
were used to derive the primary requirement that drove the design.
These requirements are covered in the next section.
These use cases also help in understanding the applicability of this
specification to real world situations.
3.1. Offline Use Cases
This section describes the use cases relating to offline transport of
keys from one system to another, using some form of export and import
model.
3.1.1. Key migration by end-user
A user wants to migrate a key from one authentication token
(container) to a different authentication token. For example, the
authentication tokens may be soft tokens on two different systems
(computers or mobile phones). The user can export the key and
related data in a standard format for import into the other
authentication token.
The key protection mechanism may rely on password-based encryption
for soft tokens, a pre-placed hardware-protected transfer key shared
between the two systems or may also rely on asymmetric keys/ PKI if
available.
3.1.2. Bulk import of new keys
Tokens are manufactured in bulk and associated keys and algorithm
data need to be loaded into the validation system through a file on
portable media. The manufacturer provides the keys and related data
in the form of a file containing records in standard format,
typically on a CD. Note that the token manufacturer and the vendor
for the validation system may be the same or different.
In this case the file usually is protected by a symmetric transport
key which was communicated separately outside of the file between the
two parties.
Some devices will allow local PIN management (the device will have a
PIN pad) hence random initial PINs set at manufacturing should be
transmitted together with the respective keys they protect.
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3.1.3. Bulk migration of existing keys
An enterprise wants to port keys and related data from an existing
validation system A into a different validation system B. The
existing validation system provides the enterprise with a
functionality that enables export of keys and related data (e.g. for
OTP tokens) in a standard format. Since the OTP tokens are in the
standard format, the enterprise can import the token records into the
new validation system B and start using the existing tokens. Note
that the vendors for the two validation systems may be the same or
different.
In this case the file usually is protected by a symmetric transport
key which was communicated separately outside of the file between the
two validation systems.
In this case it is also important to be able to communicate the
existing assignment (binding) of a device to a specific user.
3.1.4. Key upload case
User wants to activate and use a new key and related data against a
validation system that is not aware of this key. This key may be
embedded in the authentication token (e.g. SD card, USB drive) that
the user has purchased at the local electronics retailer. Along with
the authentication token, the user may get the key on a CD or a
floppy in a standard format. The user can now upload via a secure
online channel or import this key and related data into the new
validation system and start using the key.
The key protection mechanism may rely on password-based encryption,
or a pre-placed hardware-protected transfer key shared between the
token manufacturer and the validation system(s) if available.
3.2. Online Use Cases
This section describes the use cases related to provisioning the keys
using some form of a online provisioning protocol.
3.2.1. Online provisioning a key to end-user's authentication token
A mobile device user wants to obtain an OTP key for use with an OTP
soft token on the device. The soft token client from vendor A
initiates the provisioning process against a provisioning system from
vendor B using a standards-based provisioning protocol such as
[DSKPP]. The provisioning system delivers one or more keys in a
standard format that can be processed by the mobile device. The user
can download a payload that contains more than one key.
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In a variation of the above, instead of the user's mobile phone, a
key is provisioned in the user's soft token application on a laptop
using a network-based online protocol. As before, the provisioning
system delivers an OTP key in a standard format that can be processed
by the soft token on the PC.
3.2.2. Server to server provisioning of keys
Sometimes, instead of importing keys from a manufacturer using a
file, an OTP validation server may download the keys using an online
protocol. The keys can be downloaded in a standard format that can
be processed by a validation system.
In another scenario, an OTA (over-the-air) key provisioning gateway
that provisions keys to mobile phones may obtain key material from a
key issuer using an online protocol. The keys are delivered in a
standard format that can be processed by the OTA key provisioning
gateway and subsequently sent to the end-user's mobile phone.
3.2.3. Online update of an existing authentication token key
The end-user or the key issuer wants to update or configure an
existing key in the authentication token and requests a replacement
key container. The container may or may not include a new key and
may include new or updated key attributes such as a new counter value
in HOTP key case, a modified response format or length, a new
friendly name, etc.
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4. Requirements
This section outlines the most relevant requirements that are the
basis of this work. Several of the requirements were derived from
use cases described above.
R1: The format MUST support transport of multiple types of
symmetric keys and related attributes for algorithms including
HOTP, other OTP, challenge-response, etc.
R2: The format MUST handle the symmetric key itself as well of
attributes that are typically associated with symmetric keys.
Some of these attributes may be
* Unique Key Identifier
* Issuer information
* Algorithm ID
* Algorithm mode
* Issuer Name
* Key friendly name
* Event counter value (moving factor for OTP algorithms)
* Time value
R3: The format SHOULD support both offline and online scenarios.
That is it should be serializable to a file as well as it
should be possible to use this format in online provisioning
protocols
R4: The format SHOULD allow bulk representation of symmetric keys
R5: The format SHOULD allow bulk representation of PINs related to
specific keys
R6: The format SHOULD be portable to various platforms.
Furthermore, it SHOULD be computationally efficient to process.
R7: The format MUST provide appropriate level of security in terms
of data encryption and data integrity.
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R8: For online scenarios the format SHOULD NOT rely on transport
level security (e.g., SSL/TLS) for core security requirements.
R9: The format SHOULD be extensible. It SHOULD enable extension
points allowing vendors to specify additional attributes in the
future.
R10: The format SHOULD allow for distribution of key derivation data
without the actual symmetric key itself. This is to support
symmetric key management schemes that rely on key derivation
algorithms based on a pre-placed master key. The key
derivation data typically consists of a reference to the key,
rather than the key value itself.
R11: The format SHOULD allow for additional lifecycle management
operations such as counter resynchronization. Such processes
require confidentiality between client and server, thus could
use a common secure container format, without the transfer of
key material.
R12: The format MUST support the use of pre-shared symmetric keys to
ensure confidentiality of sensitive data elements.
R13: The format MUST support a password-based encryption (PBE)
[PKCS5] scheme to ensure security of sensitive data elements.
This is a widely used method for various provisioning
scenarios.
R14: The format SHOULD support asymmetric encryption algorithms such
as RSA to ensure end-to-end security of sensitive data
elements. This is to support scenarios where a pre-set shared
encryption key is difficult to use.
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5. Portable Key container definition
The portable key container is based on an XML schema definition and
contains the following main entities:
1. KeyContainer entity as defined in Section 5.1
2. Device entity as defined in Section 5.2
3. Key entity as defined in Section 5.3
Additionally other XML schema types have been defined and are
detailed in the relevant subsections of this document
A KeyContainer MAY contain one or more Device entities. A Device MAY
contain one or more Key entities
The figure below indicates a possible relationship diagram of a
container.
--------------------------------------------
| KeyContainer |
| |
| ------------------ ----------------- |
| | Device 1 | | Device n | |
| | | | | |
| | ------------ | | ------------ | |
| | | Key 1 | | | | Key n | | |
| | ------------ | | ------------ | |
| | | | | |
| | | | | |
| | ------------ | | ------------ | |
| | | Key m | | | | Key p | | |
| | ------------ | | ------------ | |
| ------------------ ----------------- |
| |
--------------------------------------------
The following section describe in detail all the entities and related
XML schema elements and attributes:
5.1. KeyContainer
The KeyContainer represents the key container entity. A Container
MAY contain more than one Device entity; each Device entity MAY
contain more than one Key entity.
The KeyContainer is defined as follows:
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<xs:complexType name="KeyContainerType">
<xs:sequence>
<xs:element name="EncryptionKey"
type="ds:KeyInfoType" minOccurs="0"/>
<xs:element name="MACAlgorithm"
type="pskc:KeyAlgorithmType" minOccurs="0"/>
<xs:element name="Device"
type="pskc:DeviceType" maxOccurs="unbounded"/>
<xs:element name="Signature"
type="ds:SignatureType" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="Version" type="pskc:VersionType" use="required"/>
</xs:complexType>
The elements of the KeyContainer have the following meanings:
o <EncryptionKey (OPTIONAL)>, Identifies the encryption key,
algorithm and possible parameters used to protect the Secret Key
data in the container, for profile and usage please see
Section 6.1
o <MACAlgorithm (OPTIONAL)>, Identifies the algorithm used to
generate a keyed digest of the the Secret Key data values when
protection algorithms are used that do not have integrity checks.
The digest guarantees the integrity and the authenticity of the
key data. for profile and usage please see Section 6.1.1
o <Device>, the host Device for one or more Keys as defined in
Section 5.2 The KeyContainer MAY contain multiple Device data
elements, allowing for bulk provisioning of keys.
o <Signature (OPTIONAL)>, the signature value of the Container.
When the signature is applied to the entire container, it MUST use
XML Signature methods as defined in [XMLSIG]. It MAY be omitted
when application layer provisioning or transport layer
provisioning protocols provide the integrity and authenticity of
the payload between the sender and the recipient of the container.
When required, this specification recommends using a symmetric key
based signature with the same key used in the encryption of the
secret key data. The signature is enveloped.
o <Version (MANDATORY)>, the version number for the portable key
container format (the XML schema defined in this document).
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5.2. Device
The Device represents the Device entity in the Container. A Device
MAY be bound to a user and MAY contain more than one keys. It is
recommended that a key is bound to one and only one Device.
The Device is defined as follows:
<xs:complexType name="DeviceType">
<xs:sequence>
<xs:element name="DeviceId" type="pskc:DeviceIdType" minOccurs="0"/>
<xs:element name="Key" type="pskc:KeyType" maxOccurs="unbounded"/>
<xs:element name="UserId" type="xs:string" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
The elements of the Device have the following meanings:
o <DeviceId>, a unique identifier for the device, defined in
Section 5.2.1
o <Key>, represents the key entity as defined in Section 5.3
o <UserId>, optionally identifies the owner or the user of the
Device TODO
5.2.1. DeviceId
The DeviceId represents the identifying criteria to uniquely identify
the device that contains the associated keys. Since devices can come
in different form factors such as hardware tokens, smartcards, soft
tokens in a mobile phone or PC etc this type allows different
criteria to be used. Combined though the criteria MUST uniquely
identify the device. For example for hardware tokens the combination
of SerialNo and Manufacturer will uniquely identify a device but not
SerialNo alone since two different token manufacturers might issue
devices with the same serial number (similar to the IssuerDN and
serial number of a certificate). For keys hold on banking cards the
identification of the device is often done via the Primary Account
Number (PAN, the big number printed on the front of the card) and an
expiry date of the card. DeviceId is an extensible type that allows
all these different ways to uniquely identify a specific key
containing device.
The DeviceId is defined as follows:
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<xs:complexType name="DeviceIdType">
<xs:sequence>
<xs:element name="Manufacturer" type="xs:string"/>
<xs:element name="SerialNo" type="xs:string"/>
<xs:element name="Model" type="xs:string" minOccurs="0"/>
<xs:element name="IssueNo" type="xs:string" minOccurs="0"/>
<xs:element name="ExpiryDate" type="xs:dateTime" minOccurs="0"/>
<xs:element name="StartDate" type="xs:dateTime" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
The elements of DeviceId have the following meanings:
o <Manufacturer>, the manufacturer of the device.
o <SerialNo>, the serial number of the device or the PAN (primary
account number) in case of EMV (Europay-MasterCard-Visa) smart
cards.
o <Model>, the model of the device (e.g one-button-HOTP-token-V1)
o <IssueNo>, the issue number in case of smart cards with the same
PAN, equivalent to a PSN (PAN Sequence Number).
o <ExpiryDate>, the expiry date of a device (such as the one on an
EMV card,used when issue numbers are not printed on cards).
o <StartDate>, the start date of a device (such as the one on an EMV
card,used when issue numbers are not printed on cards).
5.3. Key
The Key represents the key entity in the KeyContainer. The Key is
defined as follows:
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<xs:complexType name="KeyType">
<xs:sequence>
<xs:element name="Issuer" type="xs:string" minOccurs="0"/>
<xs:element name="Usage" type="pskc:UsageType"/>
<xs:element name="CardAppPersoProfileId" type="xs:string"
minOccurs="0"/>
<xs:element name="FriendlyName" type="xs:string" minOccurs="0"/>
<xs:element name="Data" type="pskc:DataType" minOccurs="0"
maxOccurs="unbounded"/>
<xs:element name="PINPolicy" type="pskc:PINPolicyType"
minOccurs="0"/>
<xs:element name="ExpiryDate" type="xs:dateTime" minOccurs="0"/>
<xs:element name="StartDate" type="xs:dateTime" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="KeyId" type="xs:string" use="required"/>
<xs:attribute name="KeyAlgorithm" type="pskc:KeyAlgorithmType"
use="required"/>
</xs:complexType>
The attributes of the Key entity have the following meanings:
o KeyId (MANDATORY), a unique and global identifier of the symmetric
key. The identifier is defined as a string of alphanumeric
characters.
o <KeyAlgorithm (MANDATORY)>, the unique URI of the type of
algorithm to use with the secret key, for profiles are described
in Section 6.3
The elements of the Key entity have the following meanings:
o <Issuer (OPTIONAL)>, The key issuer name, this is normally the
name of the organization that issues the key to the end user of
the key. For example MyBank issuing hardware tokens to their
retail banking users 'MyBank' would be the issuer. The Issuer is
defined as a String.
o <Usage (MANDATORY)>, defines the intended usage of the key and
related metadata as defined in Section 5.3.2
o <CardAppPersoProfileId (OPTIONAL)>, A uniquie identifier used
between the sending and receiving party of the container to
establish a set of constant values related to a key that are not
transmitted via the container. For example a smart card
application personalisation profile id related to attributes
present on a smart card application that have influence when
computing a response. An example could be an EMV MasterCard CAP
[CAP] application on a card personalised with data for a specific
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batch of cards such as:
IAF Internet authentication flag
CVN Cryptogram version number, for example (MCHIP2, MCHIP4,
VISA 13, VISA14)
AIP (Application Interchange Profile), 2 bytes
TVR Terminal Verification Result, 5 bytes
CVR The card verification result
AmountOther
TransactionDate
TerminalCountryCode
TransactionCurrencyCode
AmountAuthorised
IIPB
These values are not contained within attributes in the container
but are shared between the manufacturing and the validation
service through this unique CardAppPersoProfileId. The
CardAppPersoProfileId is defined as a String.
o <FriendlyName (OPTIONAL)>, The user friendly name that is assigned
to the secret key for easy reference. The FriendlyName is defined
as a String.
o <Data (OPTIONAL)>, the element carrying the data related to the
key as defined in Section 5.3.1
o <PINPolicy (OPTIONAL)>, the policy of the PIN relating to the
usage of this key as defined in Section 5.3.4
o <ExpiryDate (OPTIONAL)>, the expiry date of the key, it MUST not
be possible to use this key after this date
o <StartDate (OPTIONAL)>, the start date of the key, it MUST not be
possible to use this key before this date
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5.3.1. Data (OPTIONAL)
Defines the data attributes of the symmetric key. Each is a name
value pair which has either a plain value (in case of no encryption)
or an encrypted value as defined in EncryptedDataType in XML
Encryption.
This is also where the key value is transported, Section 7 defines a
list of reserved attribute names.
Data element is defined as follows:
<xs:complexType name="DataType">
<xs:sequence>
<xs:choice>
<xs:element name="PlainValue" type="xs:base64Binary"/>
<xs:element name="EncryptedValue" type="xenc:EncryptedDataType"/>
</xs:choice>
<xs:element name="ValueMAC" type="xs:base64Binary" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="Name" type="xs:string" use="required"/>
</xs:complexType>
The attributes of the Data element have the following meanings:
o Name, defines the name of the name-value pair, Section 7 defines a
list of reserved attribute names
The elements of the Data element have the following meanings:
o The <PlainValue> conveys an unencrypted value of the name-value
pair in base 64 encoding.
o The <EncryptedValue> element in the DataType conveys an encrypted
value of the name-value pair inside an EncryptedDataType as
defined in XML Encryption.
o The <ValueMAC (OPTIONAL)> element in the DataType conveys a keyed
MAC value of the unencrypted data for the cases where the key
protection algorithm does not support integrity checks
5.3.2. Usage (MANDATORY)
The Usage element defines the usage attribute(s) of the key entity.
Usage is defined as follows:
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<xs:complexType name="UsageType">
<xs:sequence>
<xs:element name="ResponseFormat">
<xs:complexType>
<xs:attribute name="Format"
type="pskc:ValueFormatType" use="required"/>
<xs:attribute name="Length"
type="xs:unsignedInt" use="required"/>
<xs:attribute name="CheckDigits"
type="xs:boolean" default="false"/>
</xs:complexType>
</xs:element>
<xs:element name="ChallengeFormat" minOccurs="0">
<xs:complexType>
<xs:attribute name="Format"
type="pskc:ValueFormatType" use="required"/>
<xs:attribute name="Min"
type="xs:unsignedInt" use="required"/>
<xs:attribute name="Max"
type="xs:unsignedInt" use="required"/>
<xs:attribute name="CheckDigits"
type="xs:boolean" default="false"/>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="OTP" type="xs:boolean" default="false"/>
<xs:attribute name="CR" type="xs:boolean" default="false"/>
<xs:attribute name="Integrity" type="xs:boolean" default="false"/>
<xs:attribute name="Encrypt" type="xs:boolean" default="false"/>
<xs:attribute name="Unlock" type="xs:boolean" default="false"/>
</xs:complexType>
The attributes of the Usage element define the intended usage of the
key and are a combination of one or more of the following (set to
true):
o OTP, the key will be used for OTP generation
o CR, the key will be used for Challenge/Response purposes
o Encrypt, the key will be used for data encryption purposes
o Integrity, the key will be used to generate a keyed message digest
for data integrity or authentication purposes.
o Unlock, the key will be used for an inverse challenge response in
the case a user has locked the device by entering a wrong PIN too
many times (for devices with PIN-input capability)
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5.3.2.1. OTP and CR specific Usage elements (OPTIONAL)
When the key usage is set to OTP or CR, additional attributes MUST be
provided to support the OTP and/or the response computation as
required by the underlying algorithm and to customize or configure
the outcome of the computation (format, length and usage modes).
5.3.2.1.1. ChallengeFormat element (MANDATORY)
The ChallengeFormat element defines the characteristics of the
challenge in a CR usage scenario. The Challenge element is defined
by the following attributes:
o Format (MANDATORY)
Defines the format of the challenge accepted by the device and
MUST be one of the values defined in Section 5.3.3
o CheckDigit (OPTIONAL)
Defines if the device needs to check the appended Luhn check
digit contained in a provided challenge. This is only valid if
the Format attribute is 'DECIMAL'. Value MUST be:
TRUE device will check the appended Luhn check digit in a
provided challenge
FALSE device will not check appended Luhn check digit in
challenge
o Min (MANDATORY)
Defines the minimum size of the challenge accepted by the
device for CR mode.
If the Format attribute is 'DECIMAL', 'HEXADECIMAL' or
'ALPHANUMERIC' this value indicates the minimum number of
digits/characters.
If the Format attribute is 'BASE64' or 'BINARY', this value
indicates the minimum number of bytes of the unencoded value.
Value MUST be:
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Unsigned integer.
o Max (MANDATORY)
Defines the maximum size of the challenge accepted by the
device for CR mode.
If the Format attribute is 'DECIMAL', 'HEXADECIMAL' or
'ALPHANUMERIC' this value indicates the maximum number of
digits/characters.
If the Format attribute is 'BASE64' or 'BINARY', this value
indicates the maximum number of bytes of the unencoded value.
Value MUST be:
Unsigned integer.
5.3.2.1.2. ResponseFormat element (MANDATORY)
The ResponseFormat element defines the characteristics of the result
of a computation. This defines the format of the OTP or of the
response to a challenge. The Response attribute is defined by the
following attributes:
o Format (MANDATORY)
Defines the format of the response generated by the device and
MUST be one of the values defined in Section 5.3.3
o CheckDigit (OPTIONAL)
Defines if the device needs to append a Luhn check digit to the
response. This is only valid if the Format attribute is
'DECIMAL'. Value MUST be:
TRUE device will append a Luhn check digit to the response.
FALSE device will not append a Luhn check digit to the
response.
o Length (MANDATORY)
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Defines the length of the response generated by the device.
If the Format attribute is 'DECIMAL', 'HEXADECIMAL' or
'ALPHANUMERIC' this value indicates the number of digits/
characters.
If the Format attribute is 'BASE64' or 'BINARY', this value
indicates the number of bytes of the unencoded value.
Value MUST be:
Unsigned integer.
5.3.3. ValueFormat
The ValueFormat element defines allowed formats for challenges or
responses in OTP algorithms.
ValueFormat is defined as follows:
<simpleType name="ValueFormat">
<restriction base="string">
<enumeration value="DECIMAL"/>
<enumeration value="HEXADECIMAL"/>
<enumeration value="ALPHANUMERIC"/>
<enumeration value="BASE64"/>
<enumeration value="BINARY"/>
</restriction>
</simpleType>
DECIMAL Only numerical digits
HEXADECIMAL Hexadecimal response
ALPHANUMERIC All letters and numbers (case sensitive)
BASE64 Base 64 encoded
BINARY Binary data, this is mainly used in case of connected
devices
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5.3.4. PINPolicy
The PINPolicy element defines a mean to define how the usage of a
specific key is protected by a PIN. The PIN itself can be
transmitted using the container as another Key
PINPolicy is defined as follows:
<xs:complexType name="PINPolicyType">
<xs:sequence>
<xs:element name="PINUsageMode" type="pskc:PINUsageModeType"/>
<xs:element name="WrongPINtry" type="xs:unsignedInt"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="PINKeyId" type="xs:string" use="required"/>
</xs:complexType>
The attributes of PINPolicy have the following meaning
o PINKeyId, the unique key Id within this container that contains
the value of the PIN that protects the key
The elements of PINPolicy have the following meaning
o <PINUsageMode>, the way the PIN is used during the usage of the
key as defined in Section 5.3.4.1
o <WrongPINtry>, the number of times the PIN can be entered wrongly
before it MUST not be possible to use the key anymore
5.3.4.1. PINUsageMode
The PINUsageMode element defines how the PIN is used with a specific
key
PINUsageMode is defined as follows:
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<xs:complexType name="PINUsageModeType">
<xs:choice maxOccurs="unbounded">
<xs:element name="Local"/>
<xs:element name="Prepend"/>
<xs:element name="InAlgo"/>
</xs:choice>
</xs:complexType>
The elements of PINPolicy have the following meaning
o <Local>, the PIN is checked locally on the device before allowing
the key to be used in executing the algorithm
o <Prepend>, the PIN is prepended to the OTP or response hance it
MUST be chacked by the validation server
o <InAlgo>, the PIN is used as part of the algorithm computation
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6. Usage and profile of algorithms for the portable symmetric key
container
This section details the use of the XML encryption and XML signature
elements to protect the keys transported in the cotainer. It also
profiles the number of algorithms supported by XML encryption and XML
signature to a mandatory subset for interoperability.
When no algorithm is provided the values within the container are
unencrypted, implementations SHALL ensure the privacy of the key data
through other standard mechanisms e.g. transport level encryption.
6.1. Usage of EncryptionKey to protect keys in transit
The EncryptionKey element in the KeyContainer defines the key,
algorithm and parameters used to encrypt the Secret Key data
attributes in the Container. The encryption is applied on each
individual Secret Key data in the Container. The encryption method
MUST be the same for all Secret Key data in the container.
The following sections define specifically the different supported
means to protect the keys:
6.1.1. Protecting keys using a pre-shared key via symmetric algorithms
When protecting the payload with pre-shared keys implementations
SHOULD set the name of the specific pre-shared key in the KeyName
element of the EncryptionKey of the KeyContainer. For example:
<KeyContainer Version="1.0"
xmlns="urn:ietf:params:xml:ns:keyprov:container:1.0"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
<EncryptionKey>
<ds:KeyName>PRE_SHARED_KEY</ds:KeyName>
</EncryptionKey>
....
The following is the list of symmetric key encryption algorithm and
possible parameters used to protect the Secret Key data in the
container. Systems implementing PSKC MUST support the MANDATORY
algorithms detailed below.
The encryption algorithm URI can be one of the following.
o http://www.w3.org/2001/04/xmlenc#tripledes-cbc - MANDATORY
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o http://www.w3.org/2001/04/xmlenc#aes128-cbc - MANDATORY
o http://www.w3.org/2001/04/xmlenc#aes192-cbc - OPTIONAL
o http://www.w3.org/2001/04/xmlenc#aes256-cbc - MANDATORY
o http://www.w3.org/2001/04/xmlenc#kw-tripledes - MANDATORY
o http://www.w3.org/2001/04/xmlenc#kw-aes128 - MANDATORY
o http://www.w3.org/2001/04/xmlenc#kw-aes256 - MANDATORY
o http://www.w3.org/2001/04/xmlenc#kw-aes512 - OPTIONAL
When algorithms without integrity checks are used (e.g.
http://www.w3.org/2001/04/xmlenc#aes256-cbc) a keyed MAC value using
the same key as the encryption key SHOULD be placed in the ValueMAC
element of the Data element. In this case the MAC algorithm type
MUST be set in the MACAlgorithm element in the key container entity
as defined in Section 5.1. Implementations of PSKC MUST support the
MANDATORY MAC algorithms detailed below. The MACAlgorithm URI can be
one of the following:
o http://www.w3.org/2000/09/xmldsig#hmac-sha1 - MANDATORY
For example:
<KeyContainer Version="1.0"
xmlns="urn:ietf:params:xml:ns:keyprov:container:1.0"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
<EncryptionKey>
<ds:KeyName>PRE_SHARED_KEY</ds:KeyName>
</EncryptionKey>
<MACAlgorithm>http://www.w3.org/2000/09/xmldsig#hmac-sha1
</MACAlgorithm>
.....
6.1.2. Protecting keys using passphrase based encryption keys
To be able to support passphrase based encryption keys as defined in
PKCS#5 the following XML representation of the PBE relates parameters
have been introduced in the schema. Although the approach is
extensible implementations of PSKC MUST support the
KeyDerivationMethod algorithm URI of
http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5#pbkdf2.
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<xs:complexType name="DerivedKeyType">
<xs:sequence>
<xs:element name="KeyDerivationMethod"
type="pskc:KeyDerivationMethodType" minOccurs="0"/>
<xs:element ref="xenc:ReferenceList" minOccurs="0"/>
<xs:element name="CarriedKeyName" type="xs:string"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="Id" type="xs:ID" use="optional"/>
<xs:attribute name="Type" type="xs:anyURI" use="optional"/>
</xs:complexType>
<xs:complexType name="KeyDerivationMethodType">
<xs:sequence>
<xs:any namespace="##other" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="Algorithm" type="xs:anyURI" use="required"/>
</xs:complexType>
The attributes of the DerivedKey have the following meanings:
o ID (OPTIONAL), the unique ID for this key
o Type (OPTIONAL), TODO
The elements of the DerivedKey have the following meanings:
o <KeyDerivationMethod>: URI of the algorithms used to derive the
key e.g.
(http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5#pbkdf2)
o <ReferenceList (OPTIONAL)>: a list of IDs of the elements that
have been encrypted by this key
o <CarriedKeyName (OPTIONAL)>: friendly name of the key
When using the PKCS5 PBE algorithm
(URI=http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5#pbes2)
and related parameters, the DerivedKey element MUST be used within
the EncryptionKey element of the KeyContainer in exactly the form as
shown below:
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<?xml version="1.0" encoding="UTF-8"?>
<KeyContainer
xmlns="urn:ietf:params:xml:ns:keyprov:container:1.0"
xmlns:pkcs-5=
"http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5v2-0#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"
Version="1.0">
<EncryptionKey>
<DerivedKey Id="#Passphrase1">
<CarriedKeyName>Passphrase1</CarriedKeyName>
<KeyDerivationMethod
Algorithm=
"http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5#pbkdf2">
<Parameters xsi:type="pkcs-5:PBKDF2ParameterType">
<Salt>
<Specified>Df3dRAhjGh8=</Specified>
</Salt>
<IterationCount>2000</IterationCount>
<KeyLength>16</KeyLength>
<PRF/>
</Parameters>
</KeyDerivationMethod>
</DerivedKey>
</EncryptionKey>
....
6.2. Protecting keys using asymmetric algorithms
The following is the list of asymmetric key encryption algorithm and
possible parameters used to protect the Secret Key data in the
container. Systems implementing PSKC MUST support the MANDATORY
algorithms detailed below. The encryption algorithm URI can be one
of the following.
o http://www.w3.org/2001/04/xmlenc#rsa-1_5 - MANDATORY
o http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p - OPTIONAL
For example:
TODO
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6.3. Profile of Key Algorithm
This section profiles the type(s) of algorithm of that can be used by
the key(s) transported in the container. The following algorithm
URIs are among the default support list.
o http://www.w3.org/2001/04/xmlenc#tripledes-cbc
o http://www.w3.org/2001/04/xmlenc#aes128-cbc
o http://www.w3.org/2001/04/xmlenc#aes192-cbc
o http://www.w3.org/2001/04/xmlenc#aes256-cbc
o http://www.ietf.org/keyprov/pskc#hotp
o http://www.ietf.org/keyprov/pskc#valuecompare
6.3.1. OTP Key Algorithm Identifiers
OTP key algorithm URIs have not been defined in a commonly available
standard specification. This document defines the following URIs for
the known open standard OTP algorithms.
6.3.1.1. HOTP
Standard document: RFC4226
Identifier: http://www.ietf.org/keyprov/pskc#hotp
Note that the actual URL will be finalized once a URL for this
document is determined.
6.3.1.2. Other OTP Algorithms
An implementation should refer to vendor supplied OTP key algorithm
URIs for proprietary algorithms.
6.3.2. PIN key value compare algorithm identifier
PIN key algorithm URIs have not been defined in a commonly available
standard specification. This document defines the following URIs for
a straight value comaprison of the transported secret key data as
when required to compare a PIN.
Identifier: http://www.ietf.org/keyprov/pskc#valuecompare
Note that the actual URL will be finalized once a URL for this
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document is determined.
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7. Reserved data attribute names
The following key data attribute names have been reserved:
SECRET: the shared secret key value in binary, base64 encoded
COUNTER: the event counter for event based OTP algorithms. 8 bytes
unsigned integer in big endian (i.e. network byte order) form
base64 encoded
TIME: the time for time based OTP algorithms. 8 bytes unsigned
integer in big endian (i.e. network byte order) form base64
encoded (Number of seconds since 1970)
TIME_INTERVAL: the time interval value for time based OTP
algorithms. 8 bytes unsigned integer in big endian (i.e. network
byte order) form base64 encoded.
TIME_DRIFT: the device clock drift value for time based OTP
algorithms. The value indicates number of seconds that the device
clock may drift each day. 2 bytes unsigned integer in big endian
(i.e. network byte order) form base64 encoded.
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8. Formal Syntax
The following syntax specification uses the widely adopted XML schema
format as defined by a W3C recommendation
(http://www.w3.org/TR/xmlschema-0/). It is a complete syntax
definition in the XML Schema Definition format (XSD)
All implementations of this standard must comply with the schema
below.
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:pskc="urn:ietf:params:xml:ns:keyprov:container:1.0"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"
targetNamespace="urn:ietf:params:xml:ns:keyprov:container:1.0"
elementFormDefault="qualified" attributeFormDefault="unqualified"
version="1.0">
<xs:import namespace="http://www.w3.org/2000/09/xmldsig#"
schemaLocation=
"http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/
xmldsig-core-schema.xsd"/>
<xs:import namespace="http://www.w3.org/2001/04/xmlenc#"
schemaLocation="http://www.w3.org/TR/2002/
REC-xmlenc-core-20021210/xenc-schema.xsd"/>
<xs:complexType name="KeyContainerType">
<xs:sequence>
<xs:element name="EncryptionKey" type="ds:KeyInfoType"
minOccurs="0"/>
<xs:element name="MACAlgorithm" type="pskc:KeyAlgorithmType"
minOccurs="0"/>
<xs:element name="Device" type="pskc:DeviceType"
maxOccurs="unbounded"/>
<xs:element name="Signature" type="ds:SignatureType"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="Version" type="pskc:VersionType"
use="required"/>
</xs:complexType>
<xs:simpleType name="VersionType" final="restriction">
<xs:restriction base="xs:string">
<xs:pattern value="\d{1,2}\.\d{1,3}"/>
</xs:restriction>
</xs:simpleType>
<xs:complexType name="KeyType">
<xs:sequence>
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<xs:element name="Issuer" type="xs:string" minOccurs="0"/>
<xs:element name="Usage" type="pskc:UsageType"/>
<xs:element name="CardAppPersoProfileId" type="xs:string"
minOccurs="0"/>
<xs:element name="FriendlyName" type="xs:string"
minOccurs="0"/>
<xs:element name="Data" type="pskc:DataType" minOccurs="0"
maxOccurs="unbounded"/>
<xs:element name="PINPolicy" type="pskc:PINPolicyType"
minOccurs="0"/>
<xs:element name="ExpiryDate" type="xs:dateTime"
minOccurs="0"/>
<xs:element name="StartDate" type="xs:dateTime"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="KeyId" type="xs:string" use="required"/>
<xs:attribute name="KeyAlgorithm" type="pskc:KeyAlgorithmType"
use="required"/>
</xs:complexType>
<xs:complexType name="DerivedKeyType">
<xs:sequence>
<xs:element name="KeyDerivationMethod"
type="pskc:KeyDerivationMethodType" minOccurs="0"/>
<xs:element ref="xenc:ReferenceList" minOccurs="0"/>
<xs:element name="CarriedKeyName" type="xs:string"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="Id" type="xs:ID" use="optional"/>
<xs:attribute name="Type" type="xs:anyURI" use="optional"/>
</xs:complexType>
<xs:complexType name="KeyDerivationMethodType">
<xs:sequence>
<xs:any namespace="##other" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="Algorithm" type="xs:anyURI" use="required"/>
</xs:complexType>
<xs:complexType name="PINPolicyType">
<xs:sequence>
<xs:element name="PINUsageMode"
type="pskc:PINUsageModeType"/>
<xs:element name="WrongPINtry" type="xs:unsignedInt"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="PINKeyId" type="xs:string"
use="required"/>
</xs:complexType>
<xs:complexType name="PINUsageModeType">
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<xs:choice maxOccurs="unbounded">
<xs:element name="Local"/>
<xs:element name="Prepend"/>
<xs:element name="Embed"/>
</xs:choice>
</xs:complexType>
<xs:complexType name="DeviceIdType">
<xs:sequence>
<xs:element name="Manufacturer" type="xs:string"/>
<xs:element name="SerialNo" type="xs:string"/>
<xs:element name="Model" type="xs:string" minOccurs="0"/>
<xs:element name="IssueNo" type="xs:string" minOccurs="0"/>
<xs:element name="ExpiryDate" type="xs:dateTime" minOccurs="0"/>
<xs:element name="StartDate" type="xs:dateTime" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="DeviceType">
<xs:sequence>
<xs:element name="DeviceId" type="pskc:DeviceIdType"
minOccurs="0"/>
<xs:element name="Key" type="pskc:KeyType"
maxOccurs="unbounded"/>
<xs:element name="UserId" type="xs:string" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="UsageType">
<xs:sequence>
<xs:element name="ResponseFormat">
<xs:complexType>
<xs:attribute name="Format"
type="pskc:ValueFormatType" use="required"/>
<xs:attribute name="Length" type="xs:unsignedInt"
use="required"/>
<xs:attribute name="CheckDigits" type="xs:boolean"
default="false"/>
</xs:complexType>
</xs:element>
<xs:element name="ChallengeFormat" minOccurs="0">
<xs:complexType>
<xs:attribute name="Format"
type="pskc:ValueFormatType" use="required"/>
<xs:attribute name="Min" type="xs:unsignedInt"
use="required"/>
<xs:attribute name="Max" type="xs:unsignedInt"
use="required"/>
<xs:attribute name="CheckDigits" type="xs:boolean"
default="false"/>
</xs:complexType>
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</xs:element>
</xs:sequence>
<xs:attribute name="OTP" type="xs:boolean" default="false"/>
<xs:attribute name="CR" type="xs:boolean" default="false"/>
<xs:attribute name="Integrity" type="xs:boolean"
default="false"/>
<xs:attribute name="Encrypt" type="xs:boolean"
default="false"/>
<xs:attribute name="Unlock" type="xs:boolean"
default="false"/>
</xs:complexType>
<xs:complexType name="DataType">
<xs:sequence>
<xs:choice>
<xs:element name="PlainValue" type="xs:base64Binary"/>
<xs:element name="EncryptedValue"
type="xenc:EncryptedDataType"/>
</xs:choice>
<xs:element name="ValueMAC" type="xs:base64Binary"
minOccurs="0"/>
</xs:sequence>
<xs:attribute name="Name" type="xs:string" use="required"/>
</xs:complexType>
<xs:simpleType name="KeyAlgorithmType">
<xs:restriction base="xs:anyURI"/>
</xs:simpleType>
<xs:simpleType name="ValueFormatType">
<xs:restriction base="xs:string">
<xs:enumeration value="DECIMAL"/>
<xs:enumeration value="HEXADECIMAL"/>
<xs:enumeration value="ALPHANUMERIC"/>
<xs:enumeration value="BASE64"/>
<xs:enumeration value="BINARY"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="KeyContainer" type="pskc:KeyContainerType"/>
</xs:schema>
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9. Security Considerations
The portable key container carries sensitive information (e.g.,
cryptographic keys) and may be transported across the boundaries of
one secure perimeter to another. For example, a container residing
within the secure perimeter of a back-end provisioning server in a
secure room may be transported across the internet to an end-user
device attached to a personal computer. This means that special care
must be taken to ensure the confidentiality, integrity, and
authenticity of the information contained within.
9.1. Payload confidentiality
By design, the container allows two main approaches to guaranteeing
the confidentiality of the information it contains while transported.
First, the container key data payload may be encrypted.
In this case no transport layer security is required. However,
standard security best practices apply when selecting the strength of
the cryptographic algorithm for payload encryption. Symmetric
cryptographic cipher should be used - the longer the cryptographic
key, the stronger the protection. At the time of this writing both
3DES and AES are recommended algorithms but 3DES may be dropped in
the relatively near future. Applications concerned with algorithm
longevity are advised to use AES. In cases where the exchange of
encryption keys between the sender and the receiver is not possible,
asymmetric encryption of the secret key payload may be employed.
Similarly to symmetric key cryptography, the stronger the asymmetric
key, the more secure the protection is.
If the payload is encrypted with a method that uses one of the
password-based encryption methods provided above, the payload may be
subjected to password dictionary attacks to break the encryption
password and recover the information. Standard security best
practices for selection of strong encryption passwords apply
[Schneier].
Practical implementations should use PBESalt and PBEIterationCount
when PBE encryption is used. Different PBESalt value per key
container should be used for best protection.
The second approach to protecting the confidentiality of the payload
is based on using transport layer security. The secure channel
established between the source secure perimeter (the provisioning
server from the example above) and the target perimeter (the device
attached to the end-user computer) utilizes encryption to transport
the messages that travel across. No payload encryption is required
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in this mode. Secure channels that encrypt and digest each message
provide an extra measure of security, especially when the signature
of the payload does not encompass the entire payload.
Because of the fact that the plain text payload is protected only by
the transport layer security, practical implementation must ensure
protection against man-in-the-middle attacks [Schneier]. Validating
the secure channel end-points is critically important for eliminating
intruders that may compromise the confidentiality of the payload.
9.2. Payload integrity
The portable symmetric key container provides a mean to guarantee the
integrity of the information it contains through digital signatures.
For best security practices, the digital signature of the container
should encompass the entire payload. This provides assurances for
the integrity of all attributes. It also allows verification of the
integrity of a given payload even after the container is delivered
through the communication channel to the target perimeter and channel
message integrity check is no longer possible.
9.3. Payload authenticity
The digital signature of the payload is the primary way of showing
its authenticity. The recipient of the container may use the public
key associated with the signature to assert the authenticity of the
sender by tracing it back to a preloaded public key or certificate.
Note that the digital signature of the payload can be checked even
after the container has been delivered through the secure channel of
communication.
A weaker payload authenticity guarantee may be provided by the
transport layer if it is configured to digest each message it
transports. However, no authenticity verification is possible once
the container is delivered at the recipient end. This approach may
be useful in cases where the digital signature of the container does
not encompass the entire payload.
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10. Acknowledgements
The authors of this draft would like to thank the following people
for their contributions and support to make this a better
specification: Apostol Vassilev, Shuh Chang, Jon Martinson, Siddhart
Bajaj, Stu Veath, Kevin Lewis, Philip Hallam-Baker, Hannes
Tschofenig, Andrea Doherty, Magnus Nystrom, Tim Moses, and Anders
Rundgren.
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11. Appendix A - Example Symmetric Key Containers
All examples are syntactically correct and compatible with the XML
schema in section 7.
11.1. Symmetric Key Container with a single Non-Encrypted HOTP Secret
Key
<?xml version="1.0" encoding="UTF-8"?>
<KeyContainer Version="1.0"
xmlns="urn:ietf:params:xml:ns:keyprov:container:1.0">
<Device>
<DeviceId>
<Manufacturer>ACME</Manufacturer>
<SerialNo>0755225266</SerialNo>
</DeviceId>
<Key KeyAlgorithm="http://www.ietf.org/keyprov/pskc#hotp"
KeyId="0755225266">
<Issuer>AnIssuer</Issuer>
<Usage OTP="true">
<ResponseFormat Length="6" Format="DECIMAL"/>
</Usage>
<Data Name="COUNTER">
<PlainValue>AprkuA==</PlainValue>
</Data>
<Data Name="SECRET">
<PlainValue>/4h3rOTeBegJwGpmTTq4F+RlNR0=</PlainValue>
</Data>
<ExpiryDate>2012-12-31T00:00:00</ExpiryDate>
</Key>
</Device>
</KeyContainer>
11.2. Symmetric Key Container with a single PIN protected Non-Encrypted
HOTP Secret Key
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<?xml version="1.0" encoding="UTF-8"?>
<KeyContainer Version="1.0"
xmlns="urn:ietf:params:xml:ns:keyprov:container:1.0">
<Device>
<DeviceId>
<Manufacturer>ACME</Manufacturer>
<SerialNo>0755225266</SerialNo>
</DeviceId>
<Key KeyAlgorithm="http://www.ietf.org/keyprov/pskc#hotp"
KeyId="0755225266">
<Issuer>AnIssuer</Issuer>
<Usage OTP="true">
<ResponseFormat Length="6" Format="DECIMAL"/>
</Usage>
<Data Name="COUNTER">
<PlainValue>AprkuA==</PlainValue>
</Data>
<Data Name="SECRET">
<PlainValue>/4h3rOTeBegJwGpmTTq4F+RlNR0=</PlainValue>
</Data>
<PINPolicy PINKeyId="07552252661">
<PINUsageMode>
<Local/>
</PINUsageMode>
</PINPolicy>
</Key>
<Key KeyId="07552252661"
KeyAlgorithm="http://www.ietf.org/keyprov/pskc#pin">
<Usage>
<ResponseFormat Length="4" Format="DECIMAL"/>
</Usage>
<Data Name="SECRET">
<PlainValue>MTIzNA==</PlainValue>
</Data>
</Key>
</Device>
</KeyContainer>
11.3. Symmetric Key Container with a single AES-256-CBC Encrypted HOTP
Secret Key
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<?xml version="1.0" encoding="UTF-8"?>
<KeyContainer Version="1.0"
xmlns="urn:ietf:params:xml:ns:keyprov:container:1.0"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
<EncryptionKey>
<ds:KeyName>PRE_SHARED_KEY</ds:KeyName>
</EncryptionKey>
<MACAlgorithm>http://www.w3.org/2000/09/xmldsig#hmac-sha1
</MACAlgorithm>
<Device>
<DeviceId>
<Manufacturer>ACME</Manufacturer>
<SerialNo>0755225266</SerialNo>
</DeviceId>
<Key KeyAlgorithm="http://www.ietf.org/keyprov/pskc#hotp"
KeyId="0755225266">
<Issuer>AnIssuer</Issuer>
<Usage OTP="true">
<ResponseFormat Length="8" Format="DECIMAL"/>
</Usage>
<Data Name="COUNTER">
<PlainValue>AprkuA==</PlainValue>
</Data>
<Data Name="SECRET">
<EncryptedValue>
<xenc:EncryptionMethod
Algorithm="http://www.w3.org/2001/04/xmlenc#aes256-cbc"/>
<xenc:CipherData>
<xenc:CipherValue>
kyzrWTJuhJKQHhZtf2CWbKC5H3LdfAPvKzHHQ8SdxyE=
</xenc:CipherValue>
</xenc:CipherData>
</EncryptedValue>
<ValueMAC>cwJI898rRpGBytTqCAsegaQqPZA=</ValueMAC>
</Data>
</Key>
</Device>
</KeyContainer>
11.4. Symmetric Key Container with signature and a single Password-
based Encrypted HOTP Secret Key
<?xml version="1.0" encoding="UTF-8"?>
<pskc:KeyContainer
xmlns:pskc="urn:ietf:params:xml:ns:keyprov:container:1.0"
xmlns:pkcs-5=
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"http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5v2-0#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"
Version="1.0">
<pskc:EncryptionKey>
<pskc:DerivedKey Id="#Passphrase1">
<pskc:CarriedKeyName>Passphrase1</pskc:CarriedKeyName>
<pskc:KeyDerivationMethod
Algorithm=
"http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5#pbkdf2">
<pkcs-5:Parameters xsi:type="pkcs-5:PBKDF2ParameterType">
<Salt>
<Specified>Df3dRAhjGh8=</Specified>
</Salt>
<IterationCount>2000</IterationCount>
<KeyLength>16</KeyLength>
<PRF/>
</pkcs-5:Parameters>
</pskc:KeyDerivationMethod>
<xenc:ReferenceList>
<xenc:DataReference URI="#ED"/>
</xenc:ReferenceList>
</pskc:DerivedKey>
</pskc:EncryptionKey>
<pskc:Device>
<pskc:DeviceId>
<pskc:Manufacturer>ACME</pskc:Manufacturer>
<pskc:SerialNo>0755225266</pskc:SerialNo>
</pskc:DeviceId>
<pskc:Key KeyAlgorithm="http://www.ietf.org/keyprov/pskc#hotp"
KeyId="0755225266">
<pskc:Issuer>AnIssuer</pskc:Issuer>
<pskc:Usage OTP="true">
<pskc:ResponseFormat Length="6" Format="DECIMAL"/>
</pskc:Usage>
<pskc:Data Name="COUNTER">
<pskc:PlainValue>AprkuA==</pskc:PlainValue>
</pskc:Data>
<pskc:Data Name="SECRET">
<pskc:EncryptedValue Id="ED">
<xenc:EncryptionMethod Algorithm=
"http://www.w3.org/2001/04/xmlenc#kw-aes128"/>
<xenc:CipherData>
<xenc:CipherValue>rf4dx3rvEPO0vKtKL14NbeVu8nk=
</xenc:CipherValue>
</xenc:CipherData>
</pskc:EncryptedValue>
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</pskc:Data>
</pskc:Key>
</pskc:Device>
<pskc:Signature>
<ds:SignedInfo>
<ds:CanonicalizationMethod
Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
<ds:SignatureMethod
Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
<ds:Reference URI="">
<ds:DigestMethod Algorithm=
"http://www.w3.org/2000/09/xmldsig#sha1"/>
<ds:DigestValue>j6lwx3rvEPO0vKtMup4NbeVu8nk=</ds:DigestValue>
</ds:Reference>
</ds:SignedInfo>
<ds:SignatureValue>j6lwx3rvEPO0vKtMup4NbeVu8nk=</ds:SignatureValue>
<ds:KeyInfo>
<ds:X509Data>
<ds:X509IssuerSerial>
<ds:X509IssuerName>CN=KeyProvisioning'R'Us.com,C=US
</ds:X509IssuerName>
<ds:X509SerialNumber>12345678</ds:X509SerialNumber>
</ds:X509IssuerSerial>
</ds:X509Data>
</ds:KeyInfo>
</pskc:Signature>
</pskc:KeyContainer>
11.5. Symmetric Key Container with a single RSA 1.5 Encrypted HOTP
Secret Key
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<?xml version="1.0" encoding="UTF-8"?>
<pskc:KeyContainer Version="1.0"
xmlns:pskc="urn:ietf:params:xml:ns:keyprov:container:1.0"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
<pskc:EncryptionKey>
<ds:X509Data>
<ds:X509Certificate>miib</ds:X509Certificate>
</ds:X509Data>
</pskc:EncryptionKey>
<pskc:Device>
<pskc:DeviceId>
<pskc:Manufacturer>ACME</pskc:Manufacturer>
<pskc:SerialNo>0755225266</pskc:SerialNo>
</pskc:DeviceId>
<pskc:Key KeyAlgorithm="http://www.ietf.org/keyprov/pskc#hotp"
KeyId="0755225266">
<pskc:Issuer>AnIssuer</pskc:Issuer>
<pskc:Usage OTP="true">
<pskc:ResponseFormat Length="8" Format="DECIMAL"/>
</pskc:Usage>
<pskc:Data Name="COUNTER">
<pskc:PlainValue>AprkuA==</pskc:PlainValue>
</pskc:Data>
<pskc:Data Name="SECRET">
<pskc:EncryptedValue Id="ED">
<xenc:EncryptionMethod
Algorithm="http://www.w3.org/2001/04/xmlenc#rsa_1_5"/>
<xenc:CipherData>
<xenc:CipherValue>rf4dx3rvEPO0vKtKL14NbeVu8nk=
</xenc:CipherValue>
</xenc:CipherData>
</pskc:EncryptedValue>
</pskc:Data>
</pskc:Key>
</pskc:Device>
</pskc:KeyContainer>
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12. Normative References
[CAP] MasterCard International, "Chip Authentication Program
Functional Architecture", September 2004.
[DSKPP] "Dynamic Symmetric Key Provisioning Protocol", Internet
Draft Informational, URL: http://tools.ietf.org/wg/
keyprov/draft-doherty-keyprov-dskpp-00.txt, June 2007.
[HOTP] MRaihi, D., "HOTP: An HMAC-Based One Time Password
Algorithm", RFC 4226,
URL: http://rfc.sunsite.dk/rfc/rfc4226.html,
December 2005.
[OATH] "Initiative for Open AuTHentication",
URL: http://www.openauthentication.org.
[OATHRefArch]
OATH, "Reference Architecture",
URL: http://www.openauthentication.org, Version 1.0, 2005.
[OCRA] MRaihi, D., "OCRA: OATH Challenge Response Algorithm",
Internet Draft Informational, URL: http://www.ietf.org/
internet-drafts/
draft-mraihi-mutual-oath-hotp-variants-01.txt,
December 2005.
[PKCS1] Kaliski, B., "RFC 2437: PKCS #1: RSA Cryptography
Specifications Version 2.0.",
URL: http://www.ietf.org/rfc/rfc2437.txt, Version: 2.0,
October 1998.
[PKCS12] RSA Laboratories, "PKCS #12: Personal Information Exchange
Syntax Standard", Version 1.0,
URL: ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-12/.
[PKCS5] RSA Laboratories, "PKCS #5: Password-Based Cryptography
Standard", Version 2.0,
URL: ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-5/,
March 1999.
[RFC2119] "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997,
<http://www.ietf.org/rfc/rfc2119.txt>.
[Schneier]
Schneier, B., "Secrets and Lies: Digitial Security in a
Networked World", Wiley Computer Publishing, ISBN 0-8493-
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8253-7, 2000.
[XMLENC] Eastlake, D., "XML Encryption Syntax and Processing.",
URL: http://www.w3.org/TR/xmlenc-core/, December 2002.
[XMLSIG] Eastlake, D., "XML-Signature Syntax and Processing",
URL: http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/,
W3C Recommendation, February 2002.
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Authors' Addresses
Philip Hoyer
ActivIdentity, Inc.
109 Borough High Street
London, SE1 1NL
UK
Phone: +44 (0) 20 7744 6455
Email: Philip.Hoyer@actividentity.com
Mingliang Pei
VeriSign, Inc.
487 E. Middlefield Road
Mountain View, CA 94043
USA
Phone: +1 650 426 5173
Email: mpei@verisign.com
Salah Machani
Diversinet, Inc.
2225 Sheppard Avenue East
Suite 1801
Toronto, Ontario M2J 5C2
Canada
Phone: +1 416 756 2324 Ext. 321
Email: smachani@diversinet.com
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Hoyer, et al. Expires August 25, 2008 [Page 47]
