On Thu, Aug 11, 2016 at 11:47 AM, RFC Errata System <
rfc-editor(_at_)rfc-editor(_dot_)org> wrote:
The following errata report has been submitted for RFC5084,
"Using AES-CCM and AES-GCM Authenticated Encryption in the Cryptographic
Message Syntax (CMS)".
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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=5084&eid=4774
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Type: Technical
Reported by: QUAN NGUYEN <quannguyen(_at_)google(_dot_)com>
Section: 3.2
Original Text
-------------
aes-ICVlen AES-GCM-ICVlen DEFAULT 12
A length of 12 octets is RECOMMENDED.
Corrected Text
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aes-ICVlen AES-GCM-ICVlen DEFAULT 16
A length of 16 octets is RECOMMENDED.
Notes
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Many JCE providers including OpenJDK, BouncyCastle, Conscrypt have a bug
to use 12 bytes authentication tag (aes-ICVlen) as default if the code path
[1] uses CMS. According to Ferguson's attack (http://csrc.nist.gov/groups/
ST/toolkit/BCM/documents/comments/CWC-GCM/Ferguson2.pdf), if a user
encrypts 2^32 block length message, then 12 bytes authentication tag length
has only 96 - 32 = 64 bits security which is not good enough nowadays.
Furthermore, once a forgery happens then authentication is leaked.
Sorry, I meant "authentication *key*" is leaked.
[1] In other code paths, all providers use 16 bytes authentication tag as
default.
Instructions:
-------------
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RFC5084 (draft-ietf-smime-cms-aes-ccm-and-gcm-03)
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Title : Using AES-CCM and AES-GCM Authenticated Encryption
in the Cryptographic Message Syntax (CMS)
Publication Date : November 2007
Author(s) : R. Housley
Category : PROPOSED STANDARD
Source : S/MIME Mail Security
Area : Security
Stream : IETF
Verifying Party : IESG
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