Subject: [Cfrg] [Errata Verified] RFC7539 (4858)

From: RFC Errata System <[email-masked]>
Date: Sat, 12 Nov 2016 23:06:26 -0800 (PST)

The following errata report has been verified for RFC7539,
"ChaCha20 and Poly1305 for IETF Protocols". 

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=7539&eid=4858

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Status: Verified
Type: Technical

Reported by: Timm Korte <[email-masked]>
Date Reported: 2016-11-10
Verified by: Lars Eggert (IRSG)

Section: 2.8.

Original Text
-------------
 1.  The amount of encrypted data possible in a single invocation is
     2^32-1 blocks of 64 bytes each, because of the size of the block
     counter field in the ChaCha20 block function.  This gives a total
     of 247,877,906,880 bytes, or nearly 256 GB.

Corrected Text
--------------
 1.  The amount of encrypted data possible in a single invocation is
     2^32-1 blocks of 64 bytes each, because of the size of the block
     counter field in the ChaCha20 block function.  This gives a total
     of 274,877,906,880 bytes, or nearly 256 GB.

Notes
-----
There is an error in the result of the P_MAX = ((2^32) - 1) * 64  calculation.
The correct value is 2_74_,877,906,880 while the document states 2_47_,877,906,880.
This error has already been adopted by multiple implementations as P_MAX value.

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RFC7539 (draft-irtf-cfrg-chacha20-poly1305-10)
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Title               : ChaCha20 and Poly1305 for IETF Protocols
Publication Date    : May 2015
Author(s)           : Y. Nir, A. Langley
Category            : INFORMATIONAL
Source              : Crypto Forum Research Group
Area                : N/A
Stream              : IRTF
Verifying Party     : IRSG