## The twofish encryption algorithm: a 128-bit block cipherThe first and only guide to one of today's most important new cryptography algorithms The Twofish Encryption Algorithm A symmetric block cipher that accepts keys of any length, up to 256 bits, Twofish is among the new encryption algorithms being considered by the National Institute of Science and Technology (NIST) as a replacement for the DES algorithm. Highly secure and flexible, Twofish works extremely well with large microprocessors, 8-bit smart card microprocessors, and dedicated hardware. Now from the team who developed Twofish, this book provides you with your first detailed look at: * All aspects of Twofish's design and anatomy * Twofish performance and testing results * Step-by-step instructions on how to use it in your systems * Complete source code, in C, for implementing Twofish On the companion Web site you'll find: * A direct link to Counterpane Systems for updates on Twofish * A link to the National Institute of Science and Technology (NIST) for ongoing information about the competing technologies being considered for the Advanced Encryption Standard (AES) for the next millennium For updates on Twofish and the AES process, visit these sites: * www.wiley.com/compbooks/schneier * www.counterpane.com * www.nist.gov/aes Wiley Computer Publishing Timely.Practical.Reliable Visit our Web site at www.wiley.com/compbooks/ Visit the companion Web site at www.wiley.com/compbooks/schneier |

### From inside the book

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Page 41

In some key schedules, knowledge of a

other

and LOKI; and in others some manipulation of the

In some key schedules, knowledge of a

**round subkey**uniquely specifies bits ofother

**round subkeys**. In some ciphers the bits are just reused, as in DES, IDEA,and LOKI; and in others some manipulation of the

**round subkeys**is required to ...Page 64

8.1

discuss whether different sequences of subkeys can give equivalent encryption

functions. Recall that F' is the F function without the addition of the

, ...

8.1

**Round Subkeys**8.1.1 Equivalence of**Round Subkeys**In this section, wediscuss whether different sequences of subkeys can give equivalent encryption

functions. Recall that F' is the F function without the addition of the

**round subkeys**, ...

Page 81

9.1.3 Attacking Twofish with Fixed S and no Whitening In this Twofish variant, all

key material is in the

pairs from this Twofish variant with ten rounds. We label the four words of the

data ...

9.1.3 Attacking Twofish with Fixed S and no Whitening In this Twofish variant, all

key material is in the

**round subkeys**. We acquire about 256 plaintext/ciphertextpairs from this Twofish variant with ten rounds. We label the four words of the

data ...

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### Common terms and phrases

16 rounds 32-bit words active S-boxes addition Advances in Cryptology analysis batch bits of key block cipher Blowfish byte sequences chosen plaintexts ciphertext clock cycles compute Counterpane Systems CPUs cryptographic define difference sequence differential attack differential characteristic Differential Cryptanalysis differential patterns differential probabilities DPmax DWORD encryption and decryption endif F function family key Fast Software Encryption Feistel network fixed S-boxes four S-boxes guess Hamming weight hardware hash function implementations input difference International Workshop Proceedings key bytes key length key material key schedule key setup key sizes key-dependent S-boxes linear cryptanalysis LPmax MDS matrix MDS matrix multiply number of rounds output difference p#efine pair of keys Pentium performance permutations possible PPro/II precomputed properties qo and q random related-key attack right pair round function round subkeys smart card speed Springer-Verlag structure Table Twofish Twofish variant weak keys whitening XOR difference XORed zero