PDF files with the same SHA-1 hash in roughly 263.1 SHA-1 evaluations. This attack is about 100,000 times faster than brute forcing a SHA-1 collision with a birthday attack, which was estimated to take 280 SHA-1 evaluations. The attack required "the equivalent processing power of 6,500 years of single-CPU computations and 110 years of single-GPU computations". Birthday-Near-Collision Attack – first practical chosen-prefix attack On 24 April 2019 a paper by Gaëtan Leurent and Thomas Peyrin presented at Eurocrypt 2019 described an enhancement to the previously best chosen-prefix attack in Merkle–Damgård–like digest functions based on Davies–Meyer block ciphers. With these improvements, this method is capable of finding chosen-prefix collisions in approximately 268 SHA-1 evaluations. This is approximately 1 billion times faster (and now usable for many targeted attacks, thanks to the possibility of choosing a prefix, for example malicious code or faked identities in signed certificates) than the previous attack's 277.1 evaluations (but without chosen prefix, which was impractical for most targeted attacks because the found collisions were almost random) and is fast enough to be practical for resourceful attackers, requiring approximately $100,000 of cloud processing. This method is also capable of finding chosen-prefix collisions in the MD5 function, but at a complexity of 246.3 does not surpass the prior best available method at a theoretical level (239), though potentially at a practical level (≤249). This attack has a memory requirement of 500+ GB. On 5 January 2020 the authors published an improved attack. In this paper they demonstrate a chosen-prefix collision attack with a complexity of 263.4, that at the time of publication would cost 45k USD per generated collision. Official validation Implementations of all FIPS-approved security functions can be officially validated through the CMVP program, jointly run by the National Institute of Standards and Technology (NIST) and the Communications Security Establishment (CSE). For informal verification, a package to generate a high number of test vectors is made available for download on the NIST site; the resulting verification, however, does not replace the formal CMVP validation, which is required by law for certain applications. , there are over 2000 validated implementations of SHA-1, with 14 of them capable of handling messages with a length in bits not a multiple of eight (see SHS Validation List ). Examples and pseudocode Example hashes These are examples of SHA-1 message digests in hexadecimal and in Base64 binary to ASCII text encoding. SHA1("The quick