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[TLS] [Technical Errata Reported] RFC7905 (5251)

RFC Errata System <rfc-editor@rfc-editor.org> Thu, 01 February 2018 13:59 UTC

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Subject: [TLS] [Technical Errata Reported] RFC7905 (5251)
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The following errata report has been submitted for RFC7905,
"ChaCha20-Poly1305 Cipher Suites for Transport Layer Security (TLS)".

--------------------------------------
You may review the report below and at:
http://www.rfc-editor.org/errata/eid5251

--------------------------------------
Type: Technical
Reported by: Xavier Bonnetain <xavier.bonnetain@inria.fr>

Section: 4. Security

Original Text
-------------
   Poly1305 is designed to ensure that forged messages are rejected with
   a probability of 1-(n/2^107), where n is the maximum length of the
   input to Poly1305.  In the case of (D)TLS, this means a maximum
   forgery probability of about 1 in 2^93.

Corrected Text
--------------
   Poly1305 is designed to ensure that forged messages are rejected with
   a probability of 1-(n/2^106), where n is the maximum length of the
   input to Poly1305.  In the case of (D)TLS, this means a maximum
   forgery probability of about 1 in 2^92.

Notes
-----
The security claimed on poly1305 is slightly beyond what was proven by the designer (see https://cr.yp.to/mac/poly1305-20050329.pdf), and the trivial forgery attempt with a message of length 1 succeeds with probability 2^{-106}.

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--------------------------------------
RFC7905 (draft-ietf-tls-chacha20-poly1305-04)
--------------------------------------
Title               : ChaCha20-Poly1305 Cipher Suites for Transport Layer Security (TLS)
Publication Date    : June 2016
Author(s)           : A. Langley, W. Chang, N. Mavrogiannopoulos, J. Strombergson, S. Josefsson
Category            : PROPOSED STANDARD
Source              : Transport Layer Security
Area                : Security
Stream              : IETF
Verifying Party     : IESG

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