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SHACAL is based on the following observation of SHA-1:
The hash function SHA-1 is designed around a compression function. This function takes as input a 160-bit state and a 512-bit data word and outputs a new 160-bit state. The hash function works by repeatedly calling this compression function with successive 512-bit data blocks and each time updating the state accordingly. This compression function is easily invertible if the data block is known, i.e. given the data block on which it acted and the output of the compression function, one can compute that state that went in.
SHACAL turns the SHA-1 compression function into a block cipher by using the state input as the data block and using the data input as the key input. In other words SHACAL views the SHA-1 compression function as 160-bit block cipher with a 512-bit key
Keys shorter than 512 bits are supported by padding them with zero up to 512. SHACAL is not intended to be used with keys shorter than 128 bit.
Later the same designers introduced SHACAL-2 which is similarly a 256-bit block cipher based upon the larger hash function SHA-256.
To avoid confusion, the initial SHACAL design is now called SHACAL-1.
In 2003, SHACAL-2 was selected by the NESSIE project as one of their 17 recommended algorithms.
| Block ciphers [ }|action=edit}} Edit }] |
| Algorithms: 3-Way | AES | Akelarre | Blowfish | Camellia | CAST-128 | CAST-256 | CMEA | DEAL | DES | DES-X | FEAL | FROG | G-DES | GOST | ICE | IDEA | Iraqi | KASUMI | KHAZAD | Khufu and Khafre | LOKI89/91 | LOKI97 | Lucifer | MacGuffin | Madryga | MAGENTA | MARS | MISTY1 | MMB | NewDES | RC2 | RC5 | RC6 | REDOC | Red Pike | S-1 | SAFER | SEED | Serpent | SHACAL | SHARK | Skipjack | Square | TEA | Triple DES | Twofish | XTEA |
| Design: Feistel network | Key schedule | Product cipher | S-box | SPN Attacks: Brute force | Linear / Differential cryptanalysis | Mod n | XSL Standardisation: AES process | CRYPTREC | NESSIE Misc: Avalanche effect | Block size | IV | Key size | Modes of operation | Piling-up lemma | Weak key |