Collision attack

About: Collision attack is a research topic. Over the lifetime, 1093 publications have been published within this topic receiving 28389 citations.

Investigating fundamental security requirements on whirlpool: improved preimage and collision attacks

Abstract: In this paper, improved cryptanalyses for the ISO standard hash function Whirlpool are presented with respect to the fundamental security notions. While a subspace distinguisher was presented on full version (10 rounds) of the compression function, its impact to the security of the hash function seems limited. In this paper, we discuss the (second) preimage and collision attacks for the hash function and the compression function of Whirlpool. Regarding the preimage attack, 6 rounds of the hash function are attacked with 2481 computations while the previous best attack is for 5 rounds with 2481.5 computations. Regarding the collision attack, 8 rounds of the compression function are attacked with 2120 computations, while the previous best attack is for 7 rounds with 2184 computations. To verify the correctness, especially for the rebound attack on the Sbox with an unbalanced Differential Distribution Table (DDT), the attack is partially implemented, and the differences from attacking the Sbox with balanced DDT are reported.

On authentication with HMAC and non-random properties

Abstract: MAC algorithms can provide cryptographically secure authentication services. One of the most popular algorithms in commercial applications is HMAC based on the hash functions MD5 or SHA-1. In the light of new collision search methods for members of the MD4 family including SHA-1, the security of HMAC based on these hash functions is reconsidered. We present a new method to recover both the inner- and the outer key used in HMAC when instantiated with a concrete hash function by observing text/MAC pairs. In addition to collisions, also other nonrandom properties of the hash function are used in this new attack. Among the examples of the proposed method, the first theoretical full key recovery attack on NMAC-MD5 is presented. Other examples are distinguishing, forgery and partial or full key recovery attacks on NMAC/HMAC-SHA-1 with a reduced number of steps (up to 61 out of 80). This information about the new, reduced security margin serves as an input to the selection of algorithms for authentication purposes.

Attacks on Hash Functions and Applications

Abstract: Cryptographic hash functions compute a small fixed-size hash value for any given message. A main application is in digital signatures which require that it must be hard to find collisions, i.e., two different messages that map to the same hash value. In this thesis we provide an analysis of the security of the cryptographic hash function standards MD5 and SHA-1 that have been broken since 2004 due to so called identical-prefix collision attacks. In particular, we present more efficient identical-prefix collision attacks on both MD5 and SHA-1 that improve upon the literature. Furthermore, we introduce a new more flexible attack on MD5 and SHA-1 called the chosen-prefix collision attack that allows significantly more control over the two colliding messages. Moreover, we have proven that our new attack on MD5 poses a realistic threat to the security of everyday applications with our construction of a rogue Certificat ion Authority (CA). Our rogue CA could have enabled the total subversion of secure communications with any website -- if we had not purposely crippled it. Our research has promoted the migration away from these weak hash functions towards more secure hash functions.

Cryptanalysis of a Provably Secure Cryptographic Hash Function.

Abstract: We present a cryptanalysis of a provably secure cryptographic hash function proposed by Augot, Finiasz and Sendrier in [1] Our attack is a variant of Wagner’s generalized birthday attack It is significantly faster than the attack considered in [1], and it is practical for two of the three proposed parameters

Haraka v2 – Efficient Short-Input Hashing for Post-Quantum Applications

Abstract: Recently, many efficient cryptographic hash function design strategies have been explored, not least because of the SHA-3 competition. These designs are, almost exclusively, geared towards high performance on long inputs. However, various applications exist where the performance on short (fixed length) inputs matters more. Such hash functions are the bottleneck in hash-based signature schemes like SPHINCS or XMSS, which is currently under standardization. Secure functions specifically designed for such applications are scarce. We attend to this gap by proposing two short-input hash functions (or rather simply compression functions). By utilizing AES instructions on modern CPUs, our proposals are the fastest on such platforms, reaching throughputs below one cycle per hashed byte even for short inputs, while still having a very low latency of less than 60 cycles. Under the hood, this results comes with several innovations. First, we study whether the number of rounds for our hash functions can be reduced, if only second-preimage resistance (and not collision resistance) is required. The conclusion is: only a little. Second, since their inception, AES-like designs allow for supportive security arguments by means of counting and bounding the number of active S-boxes. However, this ignores powerful attack vectors using truncated differentials, including the powerful rebound attacks. We develop a general tool-based method to include arguments against attack vectors using truncated differentials.