[Cfrg] Deoxys-II for AEAD
Thomas Peyrin <thomas.peyrin@gmail.com> Thu, 21 November 2019 17:10 UTC
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From: Thomas Peyrin <thomas.peyrin@gmail.com>
Date: Fri, 22 Nov 2019 01:10:40 +0800
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Subject: [Cfrg] Deoxys-II for AEAD
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Dear all, Following my presentation at yesterday’s CFRG meeting, we would like to propose Deoxys-II for consideration at IRTF. Deoxys-II is the winner of the CAESAR competition for Authenticated Encryption (portfolio “defense in depth”) that terminated a few months ago after a 5-year process that went through several rounds of selection (https://competitions.cr.yp.to/caesar-submissions.html). Deoxys-II is a nonce-misuse resistant beyond-birthday AEAD (Authenticated Encryption with Associated Data) scheme, with two versions: 128-bit key and 256-bit key. It is based on Deoxys-BC, a new tweakable block cipher that reuses the AES round function, and SCT-2, a nonce-misuse resistant AEAD operating mode. We believe it presents a lot of interesting features from a security and efficiency point of view. - It is a very simple, clean design, and offers a lot of flexibility - It provides full 128-bit security for both privacy and authenticity when the nonce is not reused (meaning the AE security bound is of the form O(q/2^{128}), where q is the total number of encryption or decryption queries). This is very different from block cipher-based modes such as OCB3, GCM, or AES-GCM-SIV. To give a numerical example, when encrypting 2^32 messages of 64 KB each, existing security proofs ensure that the attacker against authenticity has an advantage of at most 2^−37 for OCB3, 2^−41 for GCM, 2^-73 or AES-GCM-SIV, and 2^−94 for Deoxys-II. - Nonce-misuse resistance: Deoxys-II provides very good resistance when the nonce is reused. Actually, if the nonce is reused only a small number of times, it retains most of its full 128-bit security as the security degrades only linearly with the number of nonce repetitions. This is very different from OCB3 and GCM (for which a single nonce reuse breaks confidentiality and allows universal forgeries). Compared to AES-GCM-SIV which is also nonce-misuse resistant, Deoxys-II provides a larger security margin: for example, when encrypting 2^32 messages of 64 KB each with the same nonce, the attacker gets an advantage of about 2^−41 against AES-GCM-SIV versus 2^−51 for Deoxys-II. - Deoxys-II security has been already analyzed by the designers and by many third parties during the CAESAR competition (a few publication venue examples among several others: CRYPTO 2016, ISCAS 2017, INDOCRYPT 2017, FSE 2018, EUROCRYPT 2018, ISC 2018, 2*FSE 2019, …). One can see some of these works listed on the Deoxys website: https://sites.google.com/view/deoxyscipher This provides very strong confidence in the design. - Deoxys-II is fully parallelizable, inverse-free (no need to implement decryption for the internal tweakable block cipher) and initialization-free. It provides very good software performances, benefiting from the AES-NI instructions and general good performances of AES on any platform. Benchmarks for efficiency comparison will be produced soon, but one can expect a speed at about 1.5 AES-GCM-SIV for long messages, and about the same speed as AES-GCM-SIV for short messages. - Constant time implementations for Deoxys-II are straightforward, basically using directly bitslice implementations of AES. - A tweakable block cipher (TBC) such as Deoxys-BC is a very valuable primitive, that can be used to build easily lots of different more complex schemes, with very strong security bounds (for example, several NIST LWC candidates are based on a TBC and defining a hash out of it). To the best of our knowledge, there is no standard TBC as of today. - Deoxys-II is not covered by any patent. More details on our design, reference implementations and test vectors, can be found here: https://sites.google.com/view/deoxyscipher The Deoxys-II team.
- [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD denis bider
- Re: [Cfrg] Deoxys-II for AEAD Blumenthal, Uri - 0553 - MITLL
- Re: [Cfrg] Deoxys-II for AEAD Blumenthal, Uri - 0553 - MITLL
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Tony Arcieri
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Blumenthal, Uri - 0553 - MITLL
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Tony Arcieri
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Blumenthal, Uri - 0553 - MITLL
- Re: [Cfrg] Deoxys-II for AEAD Tony Arcieri
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Salz, Rich
- Re: [Cfrg] Deoxys-II for AEAD Vasily
- Re: [Cfrg] Deoxys-II for AEAD Thomas Peyrin
- Re: [Cfrg] Deoxys-II for AEAD Blumenthal, Uri - 0553 - MITLL