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Linux and some other Unix-like systems offer SHAcrypt modes that perform 5000 SHA256 or SHA512 hash iterations by default, with a minimum of 1000, and a maximum of 999,999,999. [17] Password Safe open-source password manager. PGP, GPG encryption software. GPG by default iterates a hash 65536 times. [18]
SHA-2: A family of two similar hash functions, with different block sizes, known as SHA-256 and SHA-512. They differ in the word size; SHA-256 uses 32-bit words where SHA-512 uses 64-bit words. There are also truncated versions of each standard, known as SHA-224, SHA-384, SHA-512/224 and SHA-512/256. These were also designed by the NSA.
In cryptanalysis and computer security, password cracking is the process of guessing passwords [1] protecting a computer system.A common approach (brute-force attack) is to repeatedly try guesses for the password and to check them against an available cryptographic hash of the password. [2]
Rainbow tables are specific to the hash function they were created for e.g., MD5 tables can crack only MD5 hashes. The theory of this technique was invented by Philippe Oechslin [ 3 ] as a fast form of time/memory tradeoff , [ 1 ] which he implemented in the Windows password cracker Ophcrack .
Hash function Security claim Best attack Publish date Comment GOST: 2 128: 2 105: 2008-08-18 Paper. [12]HAVAL-128 : 2 64: 2 7: 2004-08-17 Collisions originally reported in 2004, [13] followed up by cryptanalysis paper in 2005.
If the time to crack a password is estimated to be 100 days, password expiration times fewer than 100 days may help ensure insufficient time for an attacker. If a password has been compromised, requiring it to be changed regularly may limit the access time for the attacker.
Using SHA-1 as a hash function, the password is stretched into a 128-bit key 50,000 times before opening the document; as a result, the time required to crack it is vastly increased, similar to PBKDF2, scrypt or other KDFs. [citation needed] Office 2010 employed AES and a 128-bit key, but the number of SHA-1 conversions doubled to 100,000. [4]
SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. [3] [4] They are built using the Merkle–Damgård construction, from a one-way compression function itself built using the Davies–Meyer structure from a specialized block cipher.