55 research outputs found
Cryptanalysis of an MPEG-Video Encryption Scheme Based on Secret Huffman Tables
This paper studies the security of a recently-proposed MPEG-video encryption
scheme based on secret Huffman tables. Our cryptanalysis shows that: 1) the key
space of the encryption scheme is not sufficiently large against
divide-and-conquer (DAC) attack and known-plaintext attack; 2) it is possible
to decrypt a cipher-video with a partially-known key, thus dramatically
reducing the complexity of the DAC brute-force attack in some cases; 3) its
security against the chosen-plaintext attack is very weak. Some experimental
results are included to support the cryptanalytic results with a brief discuss
on how to improve this MPEG-video encryption scheme.Comment: 8 pages, 4 figure
APE: Authenticated Permutation-Based Encryption for Lightweight Cryptography
The domain of lightweight cryptography focuses on cryptographic algorithms for extremely constrained devices. It is very costly to avoid nonce reuse in such environments, because this requires either a hardware source of randomness, or non-volatile memory to store a counter. At the same time, a lot of cryptographic schemes actually require the nonce assumption for their security. In this paper, we propose APE as the first permutation-based authenticated encryption scheme that is resistant against nonce misuse. We formally prove that APE is secure, based on the security of the underlying permutation. To decrypt, APE processes the ciphertext blocks in reverse order, and uses inverse permutation calls. APE therefore requires a permutation that is both efficient for forward and inverse calls. We instantiate APE with the permutations of three recent lightweight hash function designs: Quark, Photon, and Spongent. For any of these permutations, an implementation that sup- ports both encryption and decryption requires less than 1.9 kGE and 2.8 kGE for 80-bit and 128-bit security levels, respectively
Improved Cryptanalysis of Skein
The hash function Skein is the submission of Ferguson et
al. to the NIST Hash Competition, and is arguably a serious candidate
for selection as SHA-3. This paper presents the rst third-party analysis
of Skein, with an extensive study of its main component: the block
cipher Three sh. We notably investigate near collisions, distinguishers,
impossible di erentials, key recovery using related-key di erential and
boomerang attacks. In particular, we present near collisions on up to 17
rounds, an impossible di erential on 21 rounds, a related-key boomerang
distinguisher on 34 rounds, a known-related-key boomerang distinguisher
on 35 rounds, and key recovery attacks on up to 32 rounds, out of 72 in
total for Threefish-512. None of our attacks directly extends to the full
Skein hash. However, the pseudorandomness of Threefish is required to
validate the security proofs on Skein, and our results conclude that at
least 3
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