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Clarify what "it" refers to #37

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2 changes: 1 addition & 1 deletion draft-irtf-cfrg-aegis-aead.md
Original file line number Diff line number Diff line change
Expand Up @@ -1576,7 +1576,7 @@ With AEGIS-256 and AEGIS-256X, random nonces can be used with no practical limit

An authentication tag may verify under multiple keys, nonces, or associated data, but AEGIS is assumed to be key committing in the receiver-binding game, preventing common attacks when used with low-entropy keys such as passwords. Finding distinct keys and/or nonces that successfully verify the same `(ad, ct, tag)` tuple is expected to require ~2<sup>64</sup> attempts with a 128-bit authentication tag and ~2<sup>128</sup> attempts with a 256-bit tag.

It is fully committing in the restricted setting where an adversary cannot control the associated data. As shown in {{IR23}}, with the ability to alter the associated data, it is possible to efficiently find multiple keys that will verify the same authenticated ciphertext.
AEGIS is fully committing in the restricted setting where an adversary cannot control the associated data. As shown in {{IR23}}, with the ability to alter the associated data, it is possible to efficiently find multiple keys that will verify the same authenticated ciphertext.

Protocols mandating a fully committing scheme without that restriction can provide the associated data as input to a cryptographic hash function and use the output as the `ad` parameter of the `Encrypt` and `Decrypt` functions. The selected hash function must ensure a minimum of 128-bit preimage resistance. An instance of such a function is SHA-256 {{!RFC6234}}.

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