*21:17* [Pub][ePrint]
Probabilistic Signature Based Framework for Differential Fault Analysis of Stream Ciphers, by Santanu Sarkar and Prakash Dey and Avishek Adhikari and Subhamoy Maitra
Differential Fault Attack (DFA) has received serious attention in cryptographic literature and very recentlysuch attacks have been mounted against several popular stream ciphers for example Grain v1, MICKEY 2.0

and Trivium, that are parts of the eStream hardware profile. The basic idea of the fault attacks consider

injection of faults and the most general set-up should consider faults at random location and random time.

Then one should identify the exact location and the exact timing of the fault (as well as multi bit faults) with the help of fault signatures.

In this paper we consider this most general set-up and solve the problem of fault attack under a general framework,

where probabilistic signatures are exploited. Our ideas subsume all the existing DFAs against the Grain family,

MICKEY 2.0 and Trivium. In the process we provide improved fault attacks for all the versions of Grain family and also

for MICKEY 2.0 (the attacks against Trivium are already quite optimal and thus there is not much scope to improve).

Our generalized method can also take care of the cases where certain parts of the keystream bits are missing

for authentication purpose. In particular, we show that the unsolved problem of identifying the faults

in random time for Grain 128a can be solved in this manner. Our techniques can easily be applied to mount fault

attack on any stream cipher of similar kind.

*21:17* [Pub][ePrint]
A flaw in a theorem about Schnorr signatures, by Daniel R. L. Brown
An alleged theorem of Neven, Smart and Warinschi (NSW) about the security of Schnorr signatures seems to have a flaw described in

this report.

Schnorr signatures require representation of an element in a

discrete logarithm group as a hashable bit string. This report

describes a defective bit string representation of elliptic curve

points. Schnorr signatures are insecure when used with this

defective representation. Nevertheless, the defective

representation meets all the conditions of the NSW theorem.

Of course, a natural representation of an elliptic curve group

element would not suffer from this major defect. So, the NSW

theorem can probably be fixed.

*21:17* [Pub][ePrint]
Equivoe-T: Transposition Equivocation Cryptography, by Gideon Samid
Plaintext is mixed with AI-generated dis-information which binds the cryptanalyst to an irreducible set of mutually exclusive plausible plaintext candidates. As impractical as Vernam \"One Time Pad\" cipher has been, it\'s security strategy: equivocation is fundamentally superior to the prevailing strategy: intractability. Intractability erodes, equivocation endures. Alas, Vernam was an overkill. Equivocation works even if only a few plaintext candidates are left as an irreducible set, which is what Equivoe-T offers.

The AI engine builds decoys off the plaintext such that each decoy has a counter-meaning, or at least an off-meaning per the guarded plaintext, while claiming at least threshold plausibility to \"pump\" entropy into the irreducible field of plaintext candidates.

Equivoe-T uses a complete transposition algorithm that guarantees the existence of a key that matches any two arbitrarily selected permutations of the n transposed elements. Therefore every decoy qualifies as a plaintext. The transposed elements may be words, letters, a mix, or otherwise. n can be selected to add intractability to the built-in equivocation since the key space grows fast (|Ktransposition| = n!).

*21:17* [Pub][ePrint]
Near Collision Side Channel Attacks, by Baris Ege and Thomas Eisenbarth and Lejla Batina
Side channel collision attacks are a powerful method to exploit side channel leakage. Otherwise than a few exceptions, collision attacks usually combine leakage from distinct points in time, making them inherently bivariate. This work introduces the notion of near collisions to exploit the fact that values depending on the same sub-key can have similar while not identical leakage. We show how such knowledge can be exploited to mount a key recovery attack. The presented approach has several desirable features when compared to other state-of-the-art collision attacks: Near collision attacks are truly univariate. They have low requirements on the leakage functions, since they work well for leakages that are linear in the bits of the targeted intermediate state. They are applicable in the presence of masking countermeasures if there exist distinguishable leakages, as in the case of leakage squeezing.

Results are backed up by a broad range of simulations for unprotected and masked implementations, as well as an analysis of the measurement set provided by DPA Contest v4.

*12:17* [Pub][ePrint]
The Norwegian Internet Voting Protocol: A new Instantiation, by Kristian Gjøsteen and Anders Smedstuen Lund
The Norwegian government ran trials of internet remote voting during the 2011 municipal elections and the 2013 parliamentary elections. From a simplified version of the voting protocol used there, the essential cryptographic operations of the voting protocol has been put together into a cryptosystem in which one can build the voting protocol on top of.This paper proposes a new instantiation of the underlying cryp- tosystem, improving our confidence in the security of the cryptosys- tem. The new instantiation is mostly similar to a previously defined instantiation, but allows parts of the security proof to be significantly improved.

*21:56* [Job][New]
Intern Software Developer (Cryptography), *CloudFlare Inc.*
CloudFlare is looking for a cryptography intern!

CloudFlare is expanding its global footprint. In order to keep our network secure we are investing in technologies to improve the security of our key management infrastructure. We are looking for an ambitious intern to help kickstart one of our cryptographic projects.

Requirements:

Experience in the theory and implementation of standard cryptographic primitives (AES, RSA, ECC)Extensive development experience in C and/or GoA deep understanding of reverse engineering techniquesAn unquenchable thirst for understanding and mitigating cryptographic attack vectorsOutside-the-box thinking and self-starter attitude

Bonus requirements:

Experience with the cryptol programming languageExperience with LLVM or other compiler technologyKnowledge of the theory and implementation of white-box cryptography

Internship length: 4-6 months.

Sound like somewhere you’d thrive? If so, then we’d love to hear from you. Send us your resume and a short paragraph introducing yourself. Please include a brief description of how you solved a customer problem or enhanced a customer\'s understanding of a technical service.

CloudFlare is a security company. All prospective employees will be subject to an extensive background check.

CloudFlare is an equal opportunity employer and does not discriminate against any employee or applicant on the basis of age, color, disability, gender, national origin, race, religion, sexual orientation, veteran status, or any classification protected by federal, state, or local law.

*15:17* [Pub][ePrint]
Algebraic partitioning: Fully compact and (almost) tightly secure cryptography, by Dennis Hofheinz
We describe a new technique for conducting ``partitioning arguments\'\'. Partitioning arguments are a popular way to prove the security of a cryptographic scheme. For instance, to prove the security of a signature scheme, a partitioning argument could divide the set of messages into ``signable\'\' messages for which a signature can be simulated during the proof, and ``unsignable\'\' ones for which any signature would allow to solve a computational problem. During the security proof, we would then hope that an adversary only requests signatures for signable messages, and later forges a signature for an unsignable one.In this work, we develop a new class of partitioning arguments from simple assumptions. Unlike previous partitioning strategies, ours is based upon an algebraic property of the partitioned elements (e.g., the signed messages), and not on their bit structure. This allows to perform the partitioning efficiently in a ``hidden\'\' way, such that already a single ``slot\'\' for a partitioning operation in the scheme can be used to implement many different partitionings sequentially, one after the other. As a consequence, we can construct complex partitionings out of simple basic (but algebraic) partitionings in a very space-efficient way.

As a demonstration of our technique, we provide the first signature and public-key encryption schemes that achieve the following properties simultaneously: they are (almost) tightly secure under a simple assumption, and they are fully compact (in the sense that parameters, keys, and signatures, resp.~ciphertexts only comprise a constant number of group elements).