INTERNET DRAFT                                             Neil Haller
draft-ietf-otp-00.txt                                         Bellcore
February 1, 1997                                            Craig Metz
                                            Kaman Sciences Corporation
                                                         Philip Nesser
                                            Nesser & Nesser Consulting

                      A One-Time Password System


  This document is an Internet Draft. Internet Drafts are working
  documents of the Internet Engineering Task Force (IETF), its Areas
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  <draft-ietf-otp-00.txt> and it expires on August 1, 1997.


  This document describes a one-time password authentication system
  (OTP). The system provides authentication for system access (login)
  and other applications requiring authentication that is secure
  against passive attacks based on replaying captured reusable
  passwords. OTP evolved from the S/KEY* One-Time Password System that
  was released by Bellcore and is described in references [3] and [5].


  One form of attack on networked computing systems is eavesdropping
  on network connections to obtain authentication information such as
  the login IDs and passwords of legitimate users. Once this
  information is captured, it can be used at a later time to gain
  access to the system. One-time password systems are designed to
  counter this type of attack, called a "replay attack" [4].

 *   S/KEY is a trademark of Bellcore

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  The authentication system described in this document uses a secret
  pass-phrase to generate a sequence of one-time (single use)
  passwords.  With this system, the user's secret pass-phrase never
  needs to cross the network at any time such as during authentication
  or during pass-phrase changes. Thus, it is not vulnerable to replay
  attacks.  Added security is provided by the property that no secret
  information need be stored on any system, including the server being

  The OTP system protects against external passive attacks against the
  authentication subsystem. It does not prevent a network eavesdropper
  from gaining access to private information and does not provide
  protection against either "social engineering" or active attacks


  There are two entities in the operation of the OTP one-time password
  system. The generator must produce the appropriate one-time password
  from the user's secret pass-phrase and from information provided in
  the challenge from the server. The server must send a challenge that
  includes the appropriate generation parameters to the generator,
  must verify the one-time password received, must store the last
  valid one-time password it received, and must store the
  corresponding one-time password sequence number. The server must
  also facilitate the changing of the user's secret pass-phrase in a
  secure manner.

  The OTP system generator passes the user's secret pass-phrase, along
  with a seed received from the server as part of the challenge,
  through multiple iterations of a secure hash function to produce a
  one-time password. After each successful authentication, the number
  of secure hash function iterations is reduced by one.  Thus, a
  unique sequence of passwords is generated.  The server verifies the
  one-time password received from the generator by computing the
  secure hash function once and comparing the result with the
  previously accepted one-time password.  This technique was first
  suggested by Leslie Lamport [1].


  In this document, the words that are used to define the significance
  of each particular requirement are usually capitalized.  These words

    - MUST

      This word or the adjective "REQUIRED" means that the item is an
      absolute requirement of the specification.

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    - SHOULD

      This word or the adjective "RECOMMENDED" means that there might
      exist valid reasons in particular circumstances to ignore this
      item, but the full implications should be understood and the
      case carefully weighed before taking a different course.

    - MAY

      This word or the adjective "OPTIONAL" means that this item is
      truly optional.  One vendor might choose to include the item
      because a particular marketplace requires it or because it
      enhances the product, for example; another vendor may omit the
      same item.


  The security of the OTP system is based on the non-invertability of
  a secure hash function. Such a function must be tractable to compute
  in the forward direction, but computationally infeasible to invert.

  The interfaces are currently defined for three such hash algorithms,
  MD4 [2] and MD5 [6] by Ronald Rivest, and SHA [7] by NIST.  All
  conforming implementations of both server and generators MUST
  support MD5.  They SHOULD support SHA and MAY also support MD4.
  Clearly, the generator and server must use the same algorithm in
  order to interoperate. Other hash algorithms may be specified for
  use with this system by publishing the appropriate interfaces.

  The secure hash algorithms listed above have the property that they
  accept an input that is arbitrarily long and produce a fixed size
  output. The OTP system folds this output to 64 bits using the
  algorithms in the Appendix A. 64 bits is also the length of the
  one-time passwords. This is believed to be long enough to be secure
  and short enough to be entered manually (see below, Form of Output)
  when necessary.


  This section describes the generation of the one-time passwords.
  This process consists of an initial step in which all inputs are
  combined, a computation step where the secure hash function is
  applied a specified number of times, and an output function where
  the 64 bit one-time password is converted to a human readable form.

  Appendix C contains examples of the outputs given a collection of
  inputs.  It provides implementors with a means of verification the
  use of these algorithms.

  Initial Step

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  In principle, the user's secret pass-phrase may be of any length. To
  reduce the risk from techniques such as exhaustive search or
  dictionary attacks, character string pass-phrases MUST contain at
  least 10 characters (see Form of Inputs below).  All implementations
  MUST support a pass-phrases of at least 63 characters.  The secret
  pass-phrase is frequently, but is not required to be, textual
  information provided by a user.

  In this step, the pass phrase is concatenated with a seed that is
  transmitted from the server in clear text. This non-secret seed
  allows clients to use the same secret pass-phrase on multiple
  machines (using different seeds) and to safely recycle their secret
  pass-phrases by changing the seed.

  The result of the concatenation is passed through the secure hash
  function and then is reduced to 64 bits using one of the function
  dependent algorithms shown in Appendix A.

  Computation Step

  A sequence of one-time passwords is produced by applying the secure
  hash function multiple times to the output of the initial step
  (called S). That is, the first one-time password to be used is
  produced by passing S through the secure hash function a number of
  times (N) specified by the user. The next one-time password to be
  used is generated by passing S though the secure hash function N-1
  times. An eavesdropper who has monitored the transmission of a one-
  time password would not be able to generate the next required
  password because doing so would mean inverting the hash function.

  Form of Inputs

  The secret pass-phrase is seen only by the OTP generator. To allow
  interchangeability of generators, all generators MUST support a
  secret pass-phrase of 10 to 63 characters. Implementations MAY
  support a longer pass-phrase, but such implementations risk the loss
  of interchangeability with implementations supporting only the

  The seed MUST consist of purely alphanumeric characters and MUST be
  of one to 16 characters in length. The seed is a string of
  characters that MUST not contain any blanks and SHOULD consist of
  strictly alphanumeric characters from the ISO-646 Invariant Code
  Set.  The seed MUST be case insensitive and MUST be internally
  converted to lower case before it is processed.

  The sequence number and seed together constitute a larger unit of
  data called the challenge. The challenge gives the generator the
  parameters it needs to calculate the correct one-time password from
  the secret pass-phrase. The challenge MUST be in a standard syntax
  so that automated generators can recognize the challenge in context

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  and extract these parameters. The syntax of the challenge is:

          otp-<algorithm identifier> <sequence integer> <seed>

  The three tokens MUST be separated by a white space (defined as any
  number of spaces and/or tabs) and the entire challenge string MUST
  be terminated with either a space or a new line. The string "otp-"
  MUST be in lower case.  The algorithm identifier is case sensitive
  (the existing identifiers are all lower case), and the seed is case
  insensitive and converted before use to lower case.  If additional
  algorithms are defined, appropriate identifiers (short, but not
  limited to three or four characters) must be defined. The currently
  defined algorithm identifiers are:

      md4        MD4 Message Digest
      md5        MD5 Message Digest
      sha1       NIST Secure Hash Algorithm Revision 1

    An example of an OTP challenge is:   otp-md5 487 dog2

    Form of Output

    The one-time password generated by the above procedure is 64 bits
    in length. Entering a 64 bit number is a difficult and error prone
    process. Some generators insert this password into the input
    stream and some others make it available for system "cut and
    paste." Still other arrangements require the one-time password to
    be entered manually. The OTP system is designed to facilitate this
    manual entry without impeding automatic methods. The one-time
    password therefore MAY be converted to, and all servers MUST be
    capable of accepting it as, a sequence of six short (1 to 4
    letter) easily typed words that only use characters from ISO-646
    IVCS. Each word is chosen from a dictionary of 2048 words; at 11
    bits per word, all one-time passwords may be encoded.

    The two extra bits in this encoding are used to store a checksum.
    The 64 bits of key are broken down into pairs of bits, then these
    pairs are summed together. The two least significant bits of this
    sum are encoded in the last two bits of the six word sequence with
    the least significant bit of the sum as the last bit encoded. All
    OTP generators MUST calculate this checksum and all OTP servers
    MUST verify this checksum explicitly as part of the operation of
    decoding this representation of the one-time password.

    Generators that produce the six-word format MUST present the words
    in upper case with single spaces used as separators. All servers
    MUST accept six-word format without regard to case and white space
    used as a separator. The two lines below represent the same one-
    time password.  The first is valid as output from a generator and
    as input a server, the second is valid only as human input to a

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          oust coat foal  mug  beak  tote

    Interoperability requires that all OTP servers and generators use
    the same dictionary. The standard dictionary was originally
    specified in the "S/KEY One Time Password System" that is
    described in RFC 1760 [5].  This dictionary is included in this
    document as Appendix D.

    To facilitate the implementation of smaller generators,
    hexadecimal output is an acceptable alternative for the
    presentation of the one-time password. All implementations of the
    server software MUST accept case-insensitive hexadecimal as well
    as six-word format. The hexadecimal digits may be separated by
    white space so servers are REQUIRED to ignore all white space.  If
    the representation is partitioned by white space, leading zeros
    must be retained. Examples of hexadecimal format are:

         Representation                Value

         3503785b369cda8b              0x3503785b369cda8b
         e5cc a1b8 7c13 096b           0xe5cca1b87c13096b
         C7 48 90 F4 27 7B A1 CF       0xc74890f4277ba1cf
         47 9 A68 28 4C 9D 0 1BC       0x479a68284c9d01bc

  In addition to accepting six-word and hexadecimal encodings of the
  64 bit one-time password, servers SHOULD accept the alternate
  dictionary encoding described in Appendix B.  The six words in this
  encoding MUST not overlap the set of words in the standard
  dictionary.  To avoid ambiguity with the hexadecimal representation,
  words in the alternate dictionary MUST not be comprised solely of
  the letters A-F.  Decoding words thus encoded does not require any
  knowledge of the alternative dictionary used so the acceptance of
  any alternate dictionary implies the acceptance of all alternate
  dictionaries.  Words in the alternative dictionaries are case
  sensitive.  Generators and servers MUST preserve the case in the
  processing of these words.

  In summary, all conforming servers MUST accept six-word input that
  uses the Standard Dictionary (RFC 1760 and Appendix D), MUST accept
  hexadecimal encoding, and SHOULD accept six-word input that uses the
  Alternative Dictionary technique (Appendix B).  As there is a remote
  possibility that a hexadecimal encoding of a one-time password will
  look like a valid six-word standard dictionary encoding, all
  implementations MUST use the following scheme.  If a six-word
  encoded one-time password is valid, it is accepted.  Otherwise, if
  the one-time password can be interpreted as hexadecimal, and with
  that decoding it is valid, then it is accepted.


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  An application on the server system that requires OTP authentication
  is expected to issue an OTP challenge as described above. Given the
  parameters from this challenge and the secret pass-phrase, the
  generator can compute (or lookup) the one-time password that is
  passed to the server to be verified.

  The server system has a database containing, for each user, the
  one-time password from the last successful authentication or the
  first OTP of a newly initialized sequence. To authenticate the user,
  the server decodes the one-time password received from the generator
  into a 64-bit key and then runs this key through the secure hash
  function once. If the result of this operation matches the stored
  previous OTP, the authentication is successful and the accepted
  one-time password is stored for future use.


  Because the number of hash function applications executed by the
  generator decreases by one each time, at some point the user must
  reinitialize the system or be unable to authenticate.

  Although some installations may not permit users to initialize
  remotely, implementations MUST provide a means to do so that does
  not reveal the user's secret pass-phrase.  One way is to provide a
  means to reinitialize the  sequence through explicit specification
  of the first one-time password.

  When the sequence of one-time passwords is reinitialized,
  implementations MUST verify that the seed or the pass-phrase is
  changed.  Installations SHOULD discourage any operation that sends
  the secret pass-phrase over a network in clear-text as such practice
  defeats the concept of a one-time password.

  Implementations MAY use the following technique for

    o  The user picks a new seed and hash count (default values may
       be offered).  The user provides these, along with the
       corresponding generated one-time password, to the host system.

    o  The user MAY also provide the corresponding generated one
       time password for count-1 as an error check.

    o  The user SHOULD provide the generated one-time password for
       the old seed and old hash count to protect an idle terminal
       or workstation (this implies that when the count is 1, the
       user can login but cannot then change the seed or count).

  In the future a specific protocol may be defined for
  reinitialization that will permit smooth and possibly automated
  interoperation of all hosts and generators.

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  All conforming server implementations MUST protect against the race
  condition described in this section.  A defense against this attack
  is outlined; implementations MAY use this approach or MAY select an
  alternative defense.

  It is possible for an attacker to listen to most of a one-time
  password, guess the remainder, and then race the legitimate user to
  complete the authentication.  Multiple guesses against the last word
  of the six-word format are likely to succeed.

  One possible defense is to prevent a user from starting multiple
  simultaneous authentication sessions. This means that once the
  legitimate user has initiated authentication, an attacker would be
  blocked until the first authentication process has completed.  In
  this approach, a timeout is necessary to thwart a denial of service


  This entire document discusses an authentication system that
  improves security by limiting the danger of eavesdropping/replay
  attacks that have been used against simple password systems [4].

  The use of the OTP system only provides protections against passive
  eavesdropping/replay attacks.  It does not provide for the privacy
  of transmitted data, and it does not provide protection against
  active attacks such as session hijacking that are known to be
  present in the current Internet [9].  The use of IP Security
  (IPsec), see [10], [11], and [12] is recommended to protect against
  TCP session hijacking.

  The success of the OTP system to protect host systems is dependent
  on the non-invertability of the secure hash functions used.  To our
  knowledge, none of the hash algorithms have been broken, but it is
  generally believed [6] that MD4 is not as strong as MD5.  If a
  server supports multiple hash algorithms, it is only as secure as
  the weakest algorithm.


  The idea behind OTP authentication was first proposed by Leslie
  Lamport [1]. Bellcore's S/KEY system, from which OTP is derived, was
  proposed by Phil Karn, who also wrote most of the Bellcore reference


  [1]  Leslie Lamport, "Password Authentication with Insecure
       Communication", Communications of the ACM 24.11 (November

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       1981), 770-772

  [2]  R. L. Rivest, The MD4 Message-Digest Algorithm, "Request For
       Comments (RFC) 1320", MIT and RSA Data Security, Inc., April

  [3]  Neil Haller, "The S/KEY One-Time Password System", Proceedings
       of the ISOC Symposium on Network and Distributed System
       Security, February 1994, San Diego, CA

  [4]  Neil Haller & Ran Atkinson, On Internet Authentication,
       "Request for Comments (RFC) 1704", Bellcore and Naval Research
       Laboratory, October 1994

  [5]  Neil Haller, The S/KEY One-Time Password System, "Request for
       Comments (RFC) 1760", Bellcore, February 1995

  [6]  R. L. Rivest, The MD5 Message-Digest Algorithm, "Request For
       Comments (RFC) 1321", MIT and RSA Data Security, Inc., April

  [7]  National Institute of Standards and Technology (NIST),
       "Announcing the Secure Hash Standard", FIPS 180-1, U.S.
       Department of Commerce, April 1995.

  [8]  International Standard - Information Processing -- ISO 7-bit
       coded character set for information interchange (Invariant Code
       Set), ISO-646, International Standards Organization, Geneva,
       Switzerland, 1983

  [9]  Computer Emergency Response Team (CERT), "IP Spoofing and
       Hijacked Terminal Connections", CA-95:01, January 1995.
       Available via anonymous ftp from in

  [10] R. Atkinson, Security Architecture for the Internet Protocol,
       "Request for Comments (RFC) 1825", Naval Research Laboratory,
       August 1995

  [11] R. Atkinson, IP Authentication Header, "Request for Comments
       (RFC) 1826", Naval Research Laboratory, August 1995

  [12] R. Atkinson, IP Encapsulating Security Payload (ESP), "Request
       for Comments (RFC) 1827", Naval Research Laboratory, August


  Neil Haller

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  MCC 1C-265B
  445 South Street
  Morristown, NJ, 07960-6438, USA

  Phone: +1 201 829-4478
  Fax:   +1 201 829-2504

  Craig Metz
  Kaman Sciences Corporation
  For NRL Code 5544
  4555 Overlook Avenue, S.W.
  Washington, DC, 20375-5337, USA

  Phone: +1 202 404-7122
  Fax:   +1 202 404-7942

  Philip J. Nesser II
  Nesser & Nesser Consulting
  13501 100th Ave NE
  Suite 5202
  Kirkland, WA 98034

  Phone: +1 206 481 4303

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        Appendix A   -   Interfaces to Secure Hash Algorithms

MD4 Message Digest (see reference [2])

          MDupdate(&md,(unsigned char *)buf,8*buflen);

          /* Fold result to 64 bits */
          md.buffer[0] ^= md.buffer[2];
          md.buffer[1] ^= md.buffer[3];

MD5 Message Digest (see reference [6])

          MD5_CTX mdCxt;


          /* Crunch the key through MD5  */
          MD5Update(&mdCxt,(unsigned char *)buf,buflen);

          /* Fold result to 64 bits */
          for( i = 0; i < 8; i++ )
              result[i] = mdCxt.digest[i] ^ mdCxt.digest[i+8];

SHA Secure Hash Algorithm (see reference [7])

          /*  Fold 160 bit result to 64 bits */
          md.buffer[0] ^= md.buffer[2];
          md.buffer[1] ^= md.buffer[3];
          md.buffer[0] ^= md.buffer[4];

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          Appendix B   -   Alternative Dictionary Algorithm

The purpose of alternative dictionary encoding of the OTP one-time
password is to allow the use of language specific or friendly words.
As case translation is not always well defined, the alternative
dictionary encoding is case sensitive.  Servers SHOULD accept this
encoding in addition to the standard 6-word and hexadecimal encodings.


  The standard 6-word encoding uses the placement of a word in the
  dictionary to represent an 11-bit number. The 64-bit one-time
  password can then be represented by six words.

  An alternative dictionary of 2048 words may be created such that
  each word W and position of the word in the dictionary N obey the

          alg( W ) % 2048 == N
          alg is the hash algorithm used (e.g. MD4, MD5, SHA1).

  In addition, no words in the standard dictionary may be chosen.

  The generator expands the 64-bit one-time password to 66 bits by
  computing parity as with the standard 6-word encoding.  The six 11-
  bit numbers are then converted to words using the dictionary that
  was created such that the above relationship holds.


  The server accepting alternative dictionary encoding converts each
  word to an 11-bit number using the above encoding. These numbers are
  then used in the same way as the decoded standard dictionary words
  to form the 66-bit one-time password.

  The server does not need to have access to the alternate dictionary
  that was used to create the one-time password it is authenticating.
  This is because the decoding from word to 11-bit number does not
  make any use of the dictionary.  As a result of the independence of
  the dictionary, a server accepting one alternate dictionary accept
  all alternate dictionaries.

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               Appendix C  -  OTP Verification Examples

This appendix provides a series of inputs and correct outputs for all
three of the defined OTP cryptographic hashes, specifically MD4, MD5,
and SHA1.  This document is intended to be used by developers for
interoperability checks when creating generators or servers.  Output
is provided in both hexadecimal notation and the six word encoding
documented in Appendix D.


Note that the output given for these checks is not intended to be
taken literally, but describes the type of action that should be

Pass Phrase Length

   Pass Phrase: Too_short
   Seed: iamvalid
   Count: 99
   Hash: ANY
   ERROR:  Pass Phrase too short

   Pass Phrase:
   Seed: iamvalid
   Count: 99
   Hash: ANY
   WARNING: Pass Phrase longer than the recommended maximum length of

Seed Values

   Pass Phrase:  A_Valid_Pass_Phrase
   Seed: Length_Okay
   Count: 99
   Hash: ANY
   ERROR: Seed must be purely alphanumeric

   Pass Phrase:  A_Valid_Pass_Phrase
   Seed: LengthOfSeventeen
   Count: 99
   Hash: ANY

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   ERROR: Seed must be between 1 and 16 characters in length

   Pass Phrase:  A_Valid_Pass_Phrase
   Seed: A Seed
   Count: 99
   Hash: ANY
   ERROR: Seed must not contain any spaces

Parity Calculations

   Pass Phrase: A_Valid_Pass_Phrase
   Seed: AValidSeed
   Count: 99
   Hash: MD5
   Hex: 85c43ee03857765b


Pass Phrase     Seed    Cnt Hex                 Six Word Format
This is a test. TeSt     0  D185 4218 EBBB 0B51 ROME MUG FRED SCAN LIVE LACE
This is a test. TeSt     1  6347 3EF0 1CD0 B444 CARD SAD MINI RYE COL KIN
This is a test. TeSt    99  C5E6 1277 6E6C 237A NOTE OUT IBIS SINK NAVE MODE
AbCdEfGhIjK     alpha1   0  5007 6F47 EB1A DE4E AWAY SEN ROOK SALT LICE MAP
AbCdEfGhIjK     alpha1   1  65D2 0D19 49B5 F7AB CHEW GRIM WU HANG BUCK SAID
AbCdEfGhIjK     alpha1  99  D150 C82C CE6F 62D1 ROIL FREE COG HUNK WAIT COCA
OTP's are good  correct  0  849C 79D4 F6F5 5388 FOOL STEM DONE TOOL BECK NILE
OTP's are good  correct  1  8C09 92FB 2508 47B1 GIST AMOS MOOT AIDS FOOD SEEM
OTP's are good  correct 99  3F3B F4B4 145F D74B TAG SLOW NOV MIN WOOL KENO


Pass Phrase     Seed    Cnt Hex                 Six Word Format
This is a test. TeSt     0  9E87 6134 D904 99DD INCH SEA ANNE LONG AHEM TOUR
This is a test. TeSt     1  7965 E054 36F5 029F EASE OIL FUM CURE AWRY AVIS
This is a test. TeSt    99  50FE 1962 C496 5880 BAIL TUFT BITS GANG CHEF THY
AbCdEfGhIjK     alpha1   0  8706 6DD9 644B F206 FULL PEW DOWN ONCE MORT ARC
AbCdEfGhIjK     alpha1   1  7CD3 4C10 40AD D14B FACT HOOF AT FIST SITE KENT

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AbCdEfGhIjK     alpha1  99  5AA3 7A81 F212 146C BODE HOP JAKE STOW JUT RAP
OTP's are good  correct  0  F205 7539 43DE 4CF9 ULAN NEW ARMY FUSE SUIT EYED
OTP's are good  correct  1  DDCD AC95 6F23 4937 SKIM CULT LOB SLAM POE HOWL
OTP's are good  correct 99  B203 E28F A525 BE47 LONG IVY JULY AJAR BOND LEE


Pass Phrase     Seed    Cnt Hex                 Six Word Format
This is a test. TeSt     0  BB9E 6AE1 979D 8FF4 MILT VARY MAST OK SEES WENT
This is a test. TeSt     1  63D9 3663 9734 385B CART OTTO HIVE ODE VAT NUT
This is a test. TeSt    99  87FE C776 8B73 CCF9 GAFF WAIT SKID GIG SKY EYED
AbCdEfGhIjK     alpha1   0  7B4C 5831 CCED CD36 LEST OR HEEL SCOT ROB SUIT
AbCdEfGhIjK     alpha1   1  D07C E229 B5CF 119B RITE TAKE GELD COST TUNE RECK
AbCdEfGhIjK     alpha1  99  27BC 7103 5AAF 3DC6 MAY STAR TIN LYON VEDA STAN
OTP's are good  correct  0  D51F 3E99 BF8E 6F0B RUST WELT KICK FELL TAIL FRAU
OTP's are good  correct  1  82AE B52D 9437 74E4 FLIT DOSE ALSO MEW DRUM DEFY
OTP's are good  correct 99  4F29 6A74 FE15 67EC AURA ALOE HURL WING BERG WAIT

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Appendix D   -   Dictionary for Converting Between 6-Word and Binary Formats

This dictionary is from the module put.c in the original Bellcore
reference distribution.

{        "A",     "ABE",   "ACE",   "ACT",   "AD",    "ADA",   "ADD",
"AGO",   "AID",   "AIM",   "AIR",   "ALL",   "ALP",   "AM",    "AMY",
"AN",    "ANA",   "AND",   "ANN",   "ANT",   "ANY",   "APE",   "APS",
"APT",   "ARC",   "ARE",   "ARK",   "ARM",   "ART",   "AS",    "ASH",
"ASK",   "AT",    "ATE",   "AUG",   "AUK",   "AVE",   "AWE",   "AWK",
"AWL",   "AWN",   "AX",   "AYE",   "BAD",   "BAG",   "BAH",   "BAM",
"BAN",   "BAR",   "BAT",   "BAY",   "BE",    "BED",   "BEE",   "BEG",
"BEN",   "BET",   "BEY",   "BIB",   "BID",   "BIG",   "BIN",   "BIT",
"BOB",   "BOG",   "BON",   "BOO",   "BOP",   "BOW",   "BOY",   "BUB",
"BUD",   "BUG",   "BUM",   "BUN",   "BUS",   "BUT",   "BUY",   "BY",
"BYE",   "CAB",   "CAL",   "CAM",   "CAN",   "CAP",   "CAR",   "CAT",
"CAW",   "COD",   "COG",   "COL",   "CON",   "COO",   "COP",   "COT",
"COW",   "COY",   "CRY",   "CUB",   "CUE",   "CUP",   "CUR",   "CUT",
"DAB",   "DAD",   "DAM",   "DAN",   "DAR",   "DAY",   "DEE",   "DEL",
"DEN",   "DES",   "DEW",   "DID",   "DIE",   "DIG",   "DIN",   "DIP",
"DO",    "DOE",   "DOG",   "DON",   "DOT",   "DOW",   "DRY",   "DUB",
"DUD",   "DUE",   "DUG",   "DUN",   "EAR",   "EAT",   "ED",    "EEL",
"EGG",   "EGO",   "ELI",   "ELK",   "ELM",   "ELY",   "EM",    "END",
"EST",   "ETC",   "EVA",   "EVE",   "EWE",   "EYE",   "FAD",   "FAN",
"FAR",   "FAT",   "FAY",   "FED",   "FEE",   "FEW",   "FIB",   "FIG",
"FIN",   "FIR",   "FIT",   "FLO",   "FLY",   "FOE",   "FOG",   "FOR",
"FRY",   "FUM",   "FUN",   "FUR",   "GAB",   "GAD",   "GAG",   "GAL",
"GAM",   "GAP",   "GAS",   "GAY",   "GEE",   "GEL",   "GEM",   "GET",
"GIG",   "GIL",   "GIN",   "GO",    "GOT",   "GUM",   "GUN",   "GUS",
"GUT",   "GUY",   "GYM",   "GYP",   "HA",    "HAD",   "HAL",   "HAM",
"HAN",   "HAP",   "HAS",   "HAT",   "HAW",   "HAY",   "HE",    "HEM",
"HEN",   "HER",   "HEW",   "HEY",   "HI",    "HID",   "HIM",   "HIP",
"HIS",   "HIT",   "HO",   "HOB",   "HOC",   "HOE",   "HOG",   "HOP",
"HOT",   "HOW",   "HUB",   "HUE",   "HUG",   "HUH",   "HUM",   "HUT",
"I",     "ICY",   "IDA",   "IF",    "IKE",   "ILL",   "INK",   "INN",
"IO",    "ION",   "IQ",   "IRA",   "IRE",   "IRK",   "IS",    "IT",
"ITS",   "IVY",   "JAB",   "JAG",   "JAM",   "JAN",   "JAR",   "JAW",
"JAY",   "JET",   "JIG",   "JIM",   "JO",    "JOB",   "JOE",   "JOG",
"JOT",   "JOY",   "JUG",   "JUT",   "KAY",   "KEG",   "KEN",   "KEY",
"KID",   "KIM",   "KIN",   "KIT",   "LA",    "LAB",   "LAC",   "LAD",
"LAG",   "LAM",   "LAP",   "LAW",   "LAY",   "LEA",   "LED",   "LEE",
"LEG",   "LEN",   "LEO",   "LET",   "LEW",   "LID",   "LIE",   "LIN",
"LIP",   "LIT",   "LO",   "LOB",   "LOG",   "LOP",   "LOS",   "LOT",
"LOU",   "LOW",   "LOY",   "LUG",   "LYE",   "MA",    "MAC",   "MAD",
"MAE",   "MAN",   "MAO",   "MAP",   "MAT",   "MAW",   "MAY",   "ME",
"MEG",   "MEL",   "MEN",   "MET",   "MEW",   "MID",   "MIN",   "MIT",
"MOB",   "MOD",   "MOE",   "MOO",   "MOP",   "MOS",   "MOT",   "MOW",
"MUD",   "MUG",   "MUM",   "MY",    "NAB",   "NAG",   "NAN",   "NAP",
"NAT",   "NAY",   "NE",   "NED",   "NEE",   "NET",   "NEW",   "NIB",

Haller, Metz, & Nesser                                       [Page 16]

INTERNET DRAFT        A One Time Password System      February 1, 1997

"NIL",   "NIP",   "NIT",   "NO",    "NOB",   "NOD",   "NON",   "NOR",
"NOT",   "NOV",   "NOW",   "NU",    "NUN",   "NUT",   "O",     "OAF",
"OAK",   "OAR",   "OAT",   "ODD",   "ODE",   "OF",    "OFF",   "OFT",
"OH",    "OIL",   "OK",   "OLD",   "ON",    "ONE",   "OR",    "ORB",
"ORE",   "ORR",   "OS",   "OTT",   "OUR",   "OUT",   "OVA",   "OW",
"OWE",   "OWL",   "OWN",   "OX",    "PA",    "PAD",   "PAL",   "PAM",
"PAN",   "PAP",   "PAR",   "PAT",   "PAW",   "PAY",   "PEA",   "PEG",
"PEN",   "PEP",   "PER",   "PET",   "PEW",   "PHI",   "PI",    "PIE",
"PIN",   "PIT",   "PLY",   "PO",    "POD",   "POE",   "POP",   "POT",
"POW",   "PRO",   "PRY",   "PUB",   "PUG",   "PUN",   "PUP",   "PUT",
"QUO",   "RAG",   "RAM",   "RAN",   "RAP",   "RAT",   "RAW",   "RAY",
"REB",   "RED",   "REP",   "RET",   "RIB",   "RID",   "RIG",   "RIM",
"RIO",   "RIP",   "ROB",   "ROD",   "ROE",   "RON",   "ROT",   "ROW",
"ROY",   "RUB",   "RUE",   "RUG",   "RUM",   "RUN",   "RYE",   "SAC",
"SAD",   "SAG",   "SAL",   "SAM",   "SAN",   "SAP",   "SAT",   "SAW",
"SAY",   "SEA",   "SEC",   "SEE",   "SEN",   "SET",   "SEW",   "SHE",
"SHY",   "SIN",   "SIP",   "SIR",   "SIS",   "SIT",   "SKI",   "SKY",
"SLY",   "SO",    "SOB",   "SOD",   "SON",   "SOP",   "SOW",   "SOY",
"SPA",   "SPY",   "SUB",   "SUD",   "SUE",   "SUM",   "SUN",   "SUP",
"TAB",   "TAD",   "TAG",   "TAN",   "TAP",   "TAR",   "TEA",   "TED",
"TEE",   "TEN",   "THE",   "THY",   "TIC",   "TIE",   "TIM",   "TIN",
"TIP",   "TO",    "TOE",   "TOG",   "TOM",   "TON",   "TOO",   "TOP",
"TOW",   "TOY",   "TRY",   "TUB",   "TUG",   "TUM",   "TUN",   "TWO",
"UN",    "UP",    "US",   "USE",   "VAN",   "VAT",   "VET",   "VIE",
"WAD",   "WAG",   "WAR",   "WAS",   "WAY",   "WE",    "WEB",   "WED",
"WEE",   "WET",   "WHO",   "WHY",   "WIN",   "WIT",   "WOK",   "WON",
"WOO",   "WOW",   "WRY",   "WU",    "YAM",   "YAP",   "YAW",   "YE",
"YEA",   "YES",   "YET",   "YOU",   "ABED",  "ABEL",  "ABET",  "ABLE",
"ABUT",  "ACHE",  "ACID",  "ACME",  "ACRE",  "ACTA",  "ACTS",  "ADAM",
"ADDS",  "ADEN",  "AFAR",  "AFRO",  "AGEE",  "AHEM",  "AHOY",  "AIDA",
"AIDE",  "AIDS",  "AIRY",  "AJAR",  "AKIN",  "ALAN",  "ALEC",  "ALGA",
"ALIA",  "ALLY",  "ALMA",  "ALOE",  "ALSO",  "ALTO",  "ALUM",  "ALVA",
"AMEN",  "AMES",  "AMID",  "AMMO",  "AMOK",  "AMOS",  "AMRA",  "ANDY",
"ANEW",  "ANNA",  "ANNE",  "ANTE",  "ANTI",  "AQUA",  "ARAB",  "ARCH",
"AREA",  "ARGO",  "ARID",  "ARMY",  "ARTS",  "ARTY",  "ASIA",  "ASKS",
"ATOM",  "AUNT",  "AURA",  "AUTO",  "AVER",  "AVID",  "AVIS",  "AVON",
"AVOW",  "AWAY",  "AWRY",  "BABE",  "BABY",  "BACH",  "BACK",  "BADE",
"BAIL",  "BAIT",  "BAKE",  "BALD",  "BALE",  "BALI",  "BALK",  "BALL",
"BALM",  "BAND",  "BANE",  "BANG",  "BANK",  "BARB",  "BARD",  "BARE",
"BARK",  "BARN",  "BARR",  "BASE",  "BASH",  "BASK",  "BASS",  "BATE",
"BATH",  "BAWD",  "BAWL",  "BEAD",  "BEAK",  "BEAM",  "BEAN",  "BEAR",
"BEAT",  "BEAU",  "BECK",  "BEEF",  "BEEN",  "BEER",  "BEET",  "BELA",
"BELL",  "BELT",  "BEND",  "BENT",  "BERG",  "BERN",  "BERT",  "BESS",
"BEST",  "BETA",  "BETH",  "BHOY",  "BIAS",  "BIDE",  "BIEN",  "BILE",
"BILK",  "BILL",  "BIND",  "BING",  "BIRD",  "BITE",  "BITS",  "BLAB",
"BLAT",  "BLED",  "BLEW",  "BLOB",  "BLOC",  "BLOT",  "BLOW",  "BLUE",
"BLUM",  "BLUR",  "BOAR",  "BOAT",  "BOCA",  "BOCK",  "BODE",  "BODY",
"BOGY",  "BOHR",  "BOIL",  "BOLD",  "BOLO",  "BOLT",  "BOMB",  "BONA",
"BOND",  "BONE",  "BONG",  "BONN",  "BONY",  "BOOK",  "BOOM",  "BOON",
"BOOT",  "BORE",  "BORG",  "BORN",  "BOSE",  "BOSS",  "BOTH",  "BOUT",
"BOWL",  "BOYD",  "BRAD",  "BRAE",  "BRAG",  "BRAN",  "BRAY",  "BRED",

Haller, Metz, & Nesser                                       [Page 17]

INTERNET DRAFT        A One Time Password System      February 1, 1997

"BREW",  "BRIG",  "BRIM",  "BROW",  "BUCK",  "BUDD",  "BUFF",  "BULB",
"BULK",  "BULL",  "BUNK",  "BUNT",  "BUOY",  "BURG",  "BURL",  "BURN",
"BURR",  "BURT",  "BURY",  "BUSH",  "BUSS",  "BUST",  "BUSY",  "BYTE",
"CADY",  "CAFE",  "CAGE",  "CAIN",  "CAKE",  "CALF",  "CALL",  "CALM",
"CAME",  "CANE",  "CANT",  "CARD",  "CARE",  "CARL",  "CARR",  "CART",
"CASE",  "CASH",  "CASK",  "CAST",  "CAVE",  "CEIL",  "CELL",  "CENT",
"CERN",  "CHAD",  "CHAR",  "CHAT",  "CHAW",  "CHEF",  "CHEN",  "CHEW",
"CHIC",  "CHIN",  "CHOU",  "CHOW",  "CHUB",  "CHUG",  "CHUM",  "CITE",
"CITY",  "CLAD",  "CLAM",  "CLAN",  "CLAW",  "CLAY",  "CLOD",  "CLOG",
"CLOT",  "CLUB",  "CLUE",  "COAL",  "COAT",  "COCA",  "COCK",  "COCO",
"CODA",  "CODE",  "CODY",  "COED",  "COIL",  "COIN",  "COKE",  "COLA",
"COLD",  "COLT",  "COMA",  "COMB",  "COME",  "COOK",  "COOL",  "COON",
"COOT",  "CORD",  "CORE",  "CORK",  "CORN",  "COST",  "COVE",  "COWL",
"CRAB",  "CRAG",  "CRAM",  "CRAY",  "CREW",  "CRIB",  "CROW",  "CRUD",
"CUBA",  "CUBE",  "CUFF",  "CULL",  "CULT",  "CUNY",  "CURB",  "CURD",
"CURE",  "CURL",  "CURT",  "CUTS",  "DADE",  "DALE",  "DAME",  "DANA",
"DANE",  "DANG",  "DANK",  "DARE",  "DARK",  "DARN",  "DART",  "DASH",
"DATA",  "DATE",  "DAVE",  "DAVY",  "DAWN",  "DAYS",  "DEAD",  "DEAF",
"DEAL",  "DEAN",  "DEAR",  "DEBT",  "DECK",  "DEED",  "DEEM",  "DEER",
"DEFT",  "DEFY",  "DELL",  "DENT",  "DENY",  "DESK",  "DIAL",  "DICE",
"DIED",  "DIET",  "DIME",  "DINE",  "DING",  "DINT",  "DIRE",  "DIRT",
"DISC",  "DISH",  "DISK",  "DIVE",  "DOCK",  "DOES",  "DOLE",  "DOLL",
"DOLT",  "DOME",  "DONE",  "DOOM",  "DOOR",  "DORA",  "DOSE",  "DOTE",
"DOUG",  "DOUR",  "DOVE",  "DOWN",  "DRAB",  "DRAG",  "DRAM",  "DRAW",
"DREW",  "DRUB",  "DRUG",  "DRUM",  "DUAL",  "DUCK",  "DUCT",  "DUEL",
"DUET",  "DUKE",  "DULL",  "DUMB",  "DUNE",  "DUNK",  "DUSK",  "DUST",
"DUTY",  "EACH",  "EARL",  "EARN",  "EASE",  "EAST",  "EASY",  "EBEN",
"ECHO",  "EDDY",  "EDEN",  "EDGE",  "EDGY",  "EDIT",  "EDNA",  "EGAN",
"ELAN",  "ELBA",  "ELLA",  "ELSE",  "EMIL",  "EMIT",  "EMMA",  "ENDS",
"ERIC",  "EROS",  "EVEN",  "EVER",  "EVIL",  "EYED",  "FACE",  "FACT",
"FADE",  "FAIL",  "FAIN",  "FAIR",  "FAKE",  "FALL",  "FAME",  "FANG",
"FARM",  "FAST",  "FATE",  "FAWN",  "FEAR",  "FEAT",  "FEED",  "FEEL",
"FEET",  "FELL",  "FELT",  "FEND",  "FERN",  "FEST",  "FEUD",  "FIEF",
"FIGS",  "FILE",  "FILL",  "FILM",  "FIND",  "FINE",  "FINK",  "FIRE",
"FIRM",  "FISH",  "FISK",  "FIST",  "FITS",  "FIVE",  "FLAG",  "FLAK",
"FLAM",  "FLAT",  "FLAW",  "FLEA",  "FLED",  "FLEW",  "FLIT",  "FLOC",
"FLOG",  "FLOW",  "FLUB",  "FLUE",  "FOAL",  "FOAM",  "FOGY",  "FOIL",
"FOLD",  "FOLK",  "FOND",  "FONT",  "FOOD",  "FOOL",  "FOOT",  "FORD",
"FORE",  "FORK",  "FORM",  "FORT",  "FOSS",  "FOUL",  "FOUR",  "FOWL",
"FRAU",  "FRAY",  "FRED",  "FREE",  "FRET",  "FREY",  "FROG",  "FROM",
"FUEL",  "FULL",  "FUME",  "FUND",  "FUNK",  "FURY",  "FUSE",  "FUSS",
"GAFF",  "GAGE",  "GAIL",  "GAIN",  "GAIT",  "GALA",  "GALE",  "GALL",
"GALT",  "GAME",  "GANG",  "GARB",  "GARY",  "GASH",  "GATE",  "GAUL",
"GAUR",  "GAVE",  "GAWK",  "GEAR",  "GELD",  "GENE",  "GENT",  "GERM",
"GETS",  "GIBE",  "GIFT",  "GILD",  "GILL",  "GILT",  "GINA",  "GIRD",
"GIRL",  "GIST",  "GIVE",  "GLAD",  "GLEE",  "GLEN",  "GLIB",  "GLOB",
"GLOM",  "GLOW",  "GLUE",  "GLUM",  "GLUT",  "GOAD",  "GOAL",  "GOAT",
"GOER",  "GOES",  "GOLD",  "GOLF",  "GONE",  "GONG",  "GOOD",  "GOOF",
"GORE",  "GORY",  "GOSH",  "GOUT",  "GOWN",  "GRAB",  "GRAD",  "GRAY",
"GREG",  "GREW",  "GREY",  "GRID",  "GRIM",  "GRIN",  "GRIT",  "GROW",
"GRUB",  "GULF",  "GULL",  "GUNK",  "GURU",  "GUSH",  "GUST",  "GWEN",

Haller, Metz, & Nesser                                       [Page 18]

INTERNET DRAFT        A One Time Password System      February 1, 1997

"GWYN",  "HAAG",  "HAAS",  "HACK",  "HAIL",  "HAIR",  "HALE",  "HALF",
"HALL",  "HALO",  "HALT",  "HAND",  "HANG",  "HANK",  "HANS",  "HARD",
"HARK",  "HARM",  "HART",  "HASH",  "HAST",  "HATE",  "HATH",  "HAUL",
"HAVE",  "HAWK",  "HAYS",  "HEAD",  "HEAL",  "HEAR",  "HEAT",  "HEBE",
"HECK",  "HEED",  "HEEL",  "HEFT",  "HELD",  "HELL",  "HELM",  "HERB",
"HERD",  "HERE",  "HERO",  "HERS",  "HESS",  "HEWN",  "HICK",  "HIDE",
"HIGH",  "HIKE",  "HILL",  "HILT",  "HIND",  "HINT",  "HIRE",  "HISS",
"HIVE",  "HOBO",  "HOCK",  "HOFF",  "HOLD",  "HOLE",  "HOLM",  "HOLT",
"HOME",  "HONE",  "HONK",  "HOOD",  "HOOF",  "HOOK",  "HOOT",  "HORN",
"HOSE",  "HOST",  "HOUR",  "HOVE",  "HOWE",  "HOWL",  "HOYT",  "HUCK",
"HUED",  "HUFF",  "HUGE",  "HUGH",  "HUGO",  "HULK",  "HULL",  "HUNK",
"HUNT",  "HURD",  "HURL",  "HURT",  "HUSH",  "HYDE",  "HYMN",  "IBIS",
"ICON",  "IDEA",  "IDLE",  "IFFY",  "INCA",  "INCH",  "INTO",  "IONS",
"IOTA",  "IOWA",  "IRIS",  "IRMA",  "IRON",  "ISLE",  "ITCH",  "ITEM",
"IVAN",  "JACK",  "JADE",  "JAIL",  "JAKE",  "JANE",  "JAVA",  "JEAN",
"JEFF",  "JERK",  "JESS",  "JEST",  "JIBE",  "JILL",  "JILT",  "JIVE",
"JOAN",  "JOBS",  "JOCK",  "JOEL",  "JOEY",  "JOHN",  "JOIN",  "JOKE",
"JOLT",  "JOVE",  "JUDD",  "JUDE",  "JUDO",  "JUDY",  "JUJU",  "JUKE",
"JULY",  "JUNE",  "JUNK",  "JUNO",  "JURY",  "JUST",  "JUTE",  "KAHN",
"KALE",  "KANE",  "KANT",  "KARL",  "KATE",  "KEEL",  "KEEN",  "KENO",
"KENT",  "KERN",  "KERR",  "KEYS",  "KICK",  "KILL",  "KIND",  "KING",
"KIRK",  "KISS",  "KITE",  "KLAN",  "KNEE",  "KNEW",  "KNIT",  "KNOB",
"KNOT",  "KNOW",  "KOCH",  "KONG",  "KUDO",  "KURD",  "KURT",  "KYLE",
"LACE",  "LACK",  "LACY",  "LADY",  "LAID",  "LAIN",  "LAIR",  "LAKE",
"LAMB",  "LAME",  "LAND",  "LANE",  "LANG",  "LARD",  "LARK",  "LASS",
"LAST",  "LATE",  "LAUD",  "LAVA",  "LAWN",  "LAWS",  "LAYS",  "LEAD",
"LEAF",  "LEAK",  "LEAN",  "LEAR",  "LEEK",  "LEER",  "LEFT",  "LEND",
"LENS",  "LENT",  "LEON",  "LESK",  "LESS",  "LEST",  "LETS",  "LIAR",
"LICE",  "LICK",  "LIED",  "LIEN",  "LIES",  "LIEU",  "LIFE",  "LIFT",
"LIKE",  "LILA",  "LILT",  "LILY",  "LIMA",  "LIMB",  "LIME",  "LIND",
"LINE",  "LINK",  "LINT",  "LION",  "LISA",  "LIST",  "LIVE",  "LOAD",
"LOAF",  "LOAM",  "LOAN",  "LOCK",  "LOFT",  "LOGE",  "LOIS",  "LOLA",
"LONE",  "LONG",  "LOOK",  "LOON",  "LOOT",  "LORD",  "LORE",  "LOSE",
"LOSS",  "LOST",  "LOUD",  "LOVE",  "LOWE",  "LUCK",  "LUCY",  "LUGE",
"LUKE",  "LULU",  "LUND",  "LUNG",  "LURA",  "LURE",  "LURK",  "LUSH",
"LUST",  "LYLE",  "LYNN",  "LYON",  "LYRA",  "MACE",  "MADE",  "MAGI",
"MAID",  "MAIL",  "MAIN",  "MAKE",  "MALE",  "MALI",  "MALL",  "MALT",
"MANA",  "MANN",  "MANY",  "MARC",  "MARE",  "MARK",  "MARS",  "MART",
"MARY",  "MASH",  "MASK",  "MASS",  "MAST",  "MATE",  "MATH",  "MAUL",
"MAYO",  "MEAD",  "MEAL",  "MEAN",  "MEAT",  "MEEK",  "MEET",  "MELD",
"MELT",  "MEMO",  "MEND",  "MENU",  "MERT",  "MESH",  "MESS",  "MICE",
"MIKE",  "MILD",  "MILE",  "MILK",  "MILL",  "MILT",  "MIMI",  "MIND",
"MINE",  "MINI",  "MINK",  "MINT",  "MIRE",  "MISS",  "MIST",  "MITE",
"MITT",  "MOAN",  "MOAT",  "MOCK",  "MODE",  "MOLD",  "MOLE",  "MOLL",
"MOLT",  "MONA",  "MONK",  "MONT",  "MOOD",  "MOON",  "MOOR",  "MOOT",
"MORE",  "MORN",  "MORT",  "MOSS",  "MOST",  "MOTH",  "MOVE",  "MUCH",
"MUCK",  "MUDD",  "MUFF",  "MULE",  "MULL",  "MURK",  "MUSH",  "MUST",
"MUTE",  "MUTT",  "MYRA",  "MYTH",  "NAGY",  "NAIL",  "NAIR",  "NAME",
"NARY",  "NASH",  "NAVE",  "NAVY",  "NEAL",  "NEAR",  "NEAT",  "NECK",
"NEED",  "NEIL",  "NELL",  "NEON",  "NERO",  "NESS",  "NEST",  "NEWS",
"NEWT",  "NIBS",  "NICE",  "NICK",  "NILE",  "NINA",  "NINE",  "NOAH",

Haller, Metz, & Nesser                                       [Page 19]

INTERNET DRAFT        A One Time Password System      February 1, 1997

"NODE",  "NOEL",  "NOLL",  "NONE",  "NOOK",  "NOON",  "NORM",  "NOSE",
"NOTE",  "NOUN",  "NOVA",  "NUDE",  "NULL",  "NUMB",  "OATH",  "OBEY",
"OBOE",  "ODIN",  "OHIO",  "OILY",  "OINT",  "OKAY",  "OLAF",  "OLDY",
"OLGA",  "OLIN",  "OMAN",  "OMEN",  "OMIT",  "ONCE",  "ONES",  "ONLY",
"ONTO",  "ONUS",  "ORAL",  "ORGY",  "OSLO",  "OTIS",  "OTTO",  "OUCH",
"OUST",  "OUTS",  "OVAL",  "OVEN",  "OVER",  "OWLY",  "OWNS",  "QUAD",
"QUIT",  "QUOD",  "RACE",  "RACK",  "RACY",  "RAFT",  "RAGE",  "RAID",
"RAIL",  "RAIN",  "RAKE",  "RANK",  "RANT",  "RARE",  "RASH",  "RATE",
"RAVE",  "RAYS",  "READ",  "REAL",  "REAM",  "REAR",  "RECK",  "REED",
"REEF",  "REEK",  "REEL",  "REID",  "REIN",  "RENA",  "REND",  "RENT",
"REST",  "RICE",  "RICH",  "RICK",  "RIDE",  "RIFT",  "RILL",  "RIME",
"RING",  "RINK",  "RISE",  "RISK",  "RITE",  "ROAD",  "ROAM",  "ROAR",
"ROBE",  "ROCK",  "RODE",  "ROIL",  "ROLL",  "ROME",  "ROOD",  "ROOF",
"ROOK",  "ROOM",  "ROOT",  "ROSA",  "ROSE",  "ROSS",  "ROSY",  "ROTH",
"ROUT",  "ROVE",  "ROWE",  "ROWS",  "RUBE",  "RUBY",  "RUDE",  "RUDY",
"RUIN",  "RULE",  "RUNG",  "RUNS",  "RUNT",  "RUSE",  "RUSH",  "RUSK",
"RUSS",  "RUST",  "RUTH",  "SACK",  "SAFE",  "SAGE",  "SAID",  "SAIL",
"SALE",  "SALK",  "SALT",  "SAME",  "SAND",  "SANE",  "SANG",  "SANK",
"SARA",  "SAUL",  "SAVE",  "SAYS",  "SCAN",  "SCAR",  "SCAT",  "SCOT",
"SEAL",  "SEAM",  "SEAR",  "SEAT",  "SEED",  "SEEK",  "SEEM",  "SEEN",
"SEES",  "SELF",  "SELL",  "SEND",  "SENT",  "SETS",  "SEWN",  "SHAG",
"SHAM",  "SHAW",  "SHAY",  "SHED",  "SHIM",  "SHIN",  "SHOD",  "SHOE",
"SHOT",  "SHOW",  "SHUN",  "SHUT",  "SICK",  "SIDE",  "SIFT",  "SIGH",
"SIGN",  "SILK",  "SILL",  "SILO",  "SILT",  "SINE",  "SING",  "SINK",
"SIRE",  "SITE",  "SITS",  "SITU",  "SKAT",  "SKEW",  "SKID",  "SKIM",
"SKIN",  "SKIT",  "SLAB",  "SLAM",  "SLAT",  "SLAY",  "SLED",  "SLEW",
"SLID",  "SLIM",  "SLIT",  "SLOB",  "SLOG",  "SLOT",  "SLOW",  "SLUG",
"SLUM",  "SLUR",  "SMOG",  "SMUG",  "SNAG",  "SNOB",  "SNOW",  "SNUB",
"SNUG",  "SOAK",  "SOAR",  "SOCK",  "SODA",  "SOFA",  "SOFT",  "SOIL",
"SOLD",  "SOME",  "SONG",  "SOON",  "SOOT",  "SORE",  "SORT",  "SOUL",
"SOUR",  "SOWN",  "STAB",  "STAG",  "STAN",  "STAR",  "STAY",  "STEM",
"STEW",  "STIR",  "STOW",  "STUB",  "STUN",  "SUCH",  "SUDS",  "SUIT",
"SULK",  "SUMS",  "SUNG",  "SUNK",  "SURE",  "SURF",  "SWAB",  "SWAG",
"SWAM",  "SWAN",  "SWAT",  "SWAY",  "SWIM",  "SWUM",  "TACK",  "TACT",
"TAIL",  "TAKE",  "TALE",  "TALK",  "TALL",  "TANK",  "TASK",  "TATE",
"TAUT",  "TEAL",  "TEAM",  "TEAR",  "TECH",  "TEEM",  "TEEN",  "TEET",
"TELL",  "TEND",  "TENT",  "TERM",  "TERN",  "TESS",  "TEST",  "THAN",
"THAT",  "THEE",  "THEM",  "THEN",  "THEY",  "THIN",  "THIS",  "THUD",
"THUG",  "TICK",  "TIDE",  "TIDY",  "TIED",  "TIER",  "TILE",  "TILL",
"TILT",  "TIME",  "TINA",  "TINE",  "TINT",  "TINY",  "TIRE",  "TOAD",
"TOGO",  "TOIL",  "TOLD",  "TOLL",  "TONE",  "TONG",  "TONY",  "TOOK",
"TOOL",  "TOOT",  "TORE",  "TORN",  "TOTE",  "TOUR",  "TOUT",  "TOWN",
"TRAG",  "TRAM",  "TRAY",  "TREE",  "TREK",  "TRIG",  "TRIM",  "TRIO",
"TROD",  "TROT",  "TROY",  "TRUE",  "TUBA",  "TUBE",  "TUCK",  "TUFT",
"TUNA",  "TUNE",  "TUNG",  "TURF",  "TURN",  "TUSK",  "TWIG",  "TWIN",
"TWIT",  "ULAN",  "UNIT",  "URGE",  "USED",  "USER",  "USES",  "UTAH",
"VAIL",  "VAIN",  "VALE",  "VARY",  "VASE",  "VAST",  "VEAL",  "VEDA",
"VEIL",  "VEIN",  "VEND",  "VENT",  "VERB",  "VERY",  "VETO",  "VICE",
"VIEW",  "VINE",  "VISE",  "VOID",  "VOLT",  "VOTE",  "WACK",  "WADE",
"WAGE",  "WAIL",  "WAIT",  "WAKE",  "WALE",  "WALK",  "WALL",  "WALT",
"WAND",  "WANE",  "WANG",  "WANT",  "WARD",  "WARM",  "WARN",  "WART",

Haller, Metz, & Nesser                                       [Page 20]

INTERNET DRAFT        A One Time Password System      February 1, 1997

"WASH",  "WAST",  "WATS",  "WATT",  "WAVE",  "WAVY",  "WAYS",  "WEAK",
"WEAL",  "WEAN",  "WEAR",  "WEED",  "WEEK",  "WEIR",  "WELD",  "WELL",
"WELT",  "WENT",  "WERE",  "WERT",  "WEST",  "WHAM",  "WHAT",  "WHEE",
"WHEN",  "WHET",  "WHOA",  "WHOM",  "WICK",  "WIFE",  "WILD",  "WILL",
"WIND",  "WINE",  "WING",  "WINK",  "WINO",  "WIRE",  "WISE",  "WISH",
"WITH",  "WOLF",  "WONT",  "WOOD",  "WOOL",  "WORD",  "WORE",  "WORK",
"WORM",  "WORN",  "WOVE",  "WRIT",  "WYNN",  "YALE",  "YANG",  "YANK",
"YARD",  "YARN",  "YAWL",  "YAWN",  "YEAH",  "YEAR",  "YELL",  "YOGA",
"YOKE"   };

Haller, Metz, & Nesser                                       [Page 21]