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In cryptography, 3-Way is a block cipher designed in 1994 by Joan Daemen, who also (with Vincent Rijmen) designed Rijndael, the winner of NIST's AES contest.

3-Way is unusual in having a fixed block size that is not a power of 2, namely 96 bits. The key length is also 96 bits. The figure 96 arises from the use of three 32 bit words in the algorithm, from which also is derived the cipher's name. When 3-Way was invented, 96 bit keys and blocks were quite strong, but many modern ciphers have a 128 bit block, and few now have keys shorter than 128 bits.

3-Way is designed to be very efficient in specialised hardware, and has some elegant mathematical features which enable nearly all the decryption to be done in exactly the same circuits as did the encryption.

Unfortunately, 3-Way is vulnerable to related key cryptanalysis; John Kelsey, Bruce Schneier and David Wagner show how it can be broken with one related key query and about chosen plaintexts.