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DKIM Crypto Update

Document Charter DKIM Crypto Update WG (dcrup)
Title DKIM Crypto Update
Last updated 2017-08-04
State Approved
WG State Concluded
IESG Responsible AD Alexey Melnikov
Charter edit AD Alexey Melnikov
Send notices to (None)

The DKIM Crypto Update (DCRUP) Working Group is chartered to update
DomainKeys Identified Mail (DKIM, RFC 6376) to handle more modern 
cryptographic algorithms and key sizes. DKIM (RFC 6376) signatures 
include a tag that identifies the hash algorithm and signing algorithm 
used in the signature. The only current algorithm is RSA, with advice 
that signing keys should be between 1024 and 2048 bits. While 1024 bit 
signatures are common, longer signatures are not because bugs in DNS 
provisioning software prevent publishing longer keys as DNS TXT records.

DKIM also currently supports use of SHA1 coupled with RSA.  SHA1 has been
formally deprecated due to weakness in numerous contexts.
The community wishes to discourage its continued use
in the DKIM context.

DCRUP will consider four types of changes to DKIM: additional signing
algorithms such as those based on elliptic curves; changes to key
strength advice and requirements; deprecating the use of SHA1;
and new public key forms, such as
putting the public key in the signature and a hash of the key in the
DNS to bypass bugs in DNS provisioning software that prevent publishing
longer keys as DNS TXT records.  Changes will be limited to existing
implemented algorithms and key forms. Other changes to DKIM, such as new
message canonicalization schemes, are out of scope.  The WG will as far 
as possible avoid changes incompatible with deployed DKIM signers and