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In cryptography
Cryptography

Cryptography is the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely with information theory, computer security and engineering....
, SAFER (Secure And Fast Encryption Routine) is the name of a family of block cipher
Block cipher

In cryptography, a block cipher is a symmetric key algorithm cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation....
s designed primarily by James Massey
James Massey

James Lee Massey is an information theorist andcryptographer, Professor Emeritus of Digital Technology at ETH Zurich. His notable workincludes the application of the Berlekamp-Massey algorithm to linear codes, the design of the block ciphers International Data Encryption Algorithm and SAFER, and the Massey-Omura cryptosystem ....
 (one of the designers of IDEA) on behalf of Cylink Corporation. The early SAFER K and SAFER SK designs share the same encryption
Encryption

In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key ....
 function, but differ in the number of rounds and the key schedule
Key schedule

In cryptography, the so-called product ciphers are a certain kind of ciphers, where the ciphering of data is done in "rounds". The general setup of each round is the same, except for some hard-coded parameters and a part of the key , called a subkey....
. More recent versions — SAFER+ and SAFER++ — were submitted as candidates to the AES process and the NESSIE
NESSIE

NESSIE was a European research project funded from 2000–2003 to identify secure cryptography Cryptographic primitive....
 project respectively.






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In cryptography
Cryptography

Cryptography is the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely with information theory, computer security and engineering....
, SAFER (Secure And Fast Encryption Routine) is the name of a family of block cipher
Block cipher

In cryptography, a block cipher is a symmetric key algorithm cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation....
s designed primarily by James Massey
James Massey

James Lee Massey is an information theorist andcryptographer, Professor Emeritus of Digital Technology at ETH Zurich. His notable workincludes the application of the Berlekamp-Massey algorithm to linear codes, the design of the block ciphers International Data Encryption Algorithm and SAFER, and the Massey-Omura cryptosystem ....
 (one of the designers of IDEA) on behalf of Cylink Corporation. The early SAFER K and SAFER SK designs share the same encryption
Encryption

In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key ....
 function, but differ in the number of rounds and the key schedule
Key schedule

In cryptography, the so-called product ciphers are a certain kind of ciphers, where the ciphering of data is done in "rounds". The general setup of each round is the same, except for some hard-coded parameters and a part of the key , called a subkey....
. More recent versions — SAFER+ and SAFER++ — were submitted as candidates to the AES process and the NESSIE
NESSIE

NESSIE was a European research project funded from 2000–2003 to identify secure cryptography Cryptographic primitive....
 project respectively. All of the algorithms in the SAFER family are unpatented and available for unrestricted use.

SAFER K and SAFER SK

Safer
The first SAFER cipher was SAFER K-64, published by Massey in 1993, with a 64-bit block size
Block size (cryptography)

In modern cryptography, symmetric key algorithm ciphers are generally divided into stream ciphers and block ciphers. Block ciphers operate on a fixed length string of bits....
. The "K-64" denotes a key size
Key size

In cryptography, key size or key length is the size of the key used in a cryptographic algorithm . An algorithm's key length is distinct from its cryptographic security, which is a logarithmic measure of the fastest known computational attack on the algorithm, also measured in bits....
 of 64 bits. There was some demand for a version with a larger 128-bit key
Key (cryptography)

In cryptography, a key is a piece of information that determines the functional output of a cryptographic algorithm or cipher. Without a key, the algorithm would have no result....
, and the following year Massey published such a variant incorporating new key schedule designed by the Singapore
Singapore

Singapore , officially the Republic of Singapore, is an island country microstate located at the southern tip of the Malay Peninsula. It lies 137 kilometres north of the equator, south of the Malaysian state of Johor and north of Indonesia's Riau Islands....
 Ministry for Home affairs: SAFER K-128. However, both Lars Knudsen
Lars Knudsen

Lars Ramkilde Knudsen is a Denmark researcher in cryptography, particularly interested in the design and cryptanalysis of block ciphers, cryptographic hash function and message authentication codes ....
 and Sean Murphy
Sean Murphy (cryptographer)

Sean Murphy is a cryptographer, currently a professor at Royal Holloway, University of London. He worked on the NESSIE and ECRYPT projects. His notable research includes the cryptanalysis of FEAL and the Advanced Encryption Standard, and the use of stochastic and statistics techniques in cryptology....
 found minor weaknesses in this version, prompting a redesign of the key schedule to one suggested by Knudsen; these variants were named SAFER SK-64 and SAFER SK-128 respectively — the "SK" standing for "Strengthened Key schedule", though the RSA
RSA Security

RSA, The Security Division of EMC Corporation, is headquartered in Bedford, Massachusetts, United States, and maintains offices in Ireland, Israel, the United Kingdom, Singapore, India, China, Hong Kong and Japan....
 FAQ reports that, "one joke has it that SK really stands for 'Stop Knudsen', a wise precaution in the design of any block cipher". Another variant with a reduced key size was published, SAFER SK-40, to comply with 40-bit
40-bit encryption

40-bit encryption refers to a key size of forty bits, or five bytes, for symmetric encryption; this represents a relatively low level of security....
 export restrictions.

All of these ciphers use the same round function consisting of four stages, as shown in the diagram: a key-mixing stage, a substitution layer, another key-mixing stage, and finally a diffusion layer. In the first key-mixing stage, the plaintext block is divided into eight 8-bit segments, and subkeys are added using either addition modulo 256 (denoted by a "+" in a square) or XOR (denoted by a "+" in a circle). The substitution layer consists of two S-boxes, each the inverse of each other, derived from discrete exponentiation
Exponentiation

Exponentiation is a mathematics operation , written 'an', involving two numbers, the base a and the exponent n....
 (45x) and logarithm
Logarithm

In mathematics, the logarithm of a number to a given base is the Power or exponent to which the base must be raised in order to produce the number....
 (log45x) functions. After a second key-mixing stage there is the diffusion layer: a novel cryptographic component termed a pseudo-Hadamard transform
Pseudo-Hadamard transform

The pseudo-Hadamard transform is a reversible transformation of a bit string that provides diffusion . See Hadamard transform.The bit string must be of even length, so it can be split into two bit strings a and b of equal lengths, each of n bits....
 (PHT). (The PHT was also later used in the Twofish
Twofish

In cryptography, Twofish is a Symmetric-key algorithm block cipher with a block size of 128 bits and key sizes up to 256 bits. It was one of the five finalists of the Advanced Encryption Standard process, but was not selected for standardisation....
 cipher.)

SAFER+ and SAFER++

There are two more-recent members of the SAFER family that have made changes to the main encryption routine, designed by the Armenian cryptographers Gurgen Khachatrian and Melsik Kuregian in conjunction with Massey.

  • SAFER+ (Massey et al, 1998) was submitted as a candidate for the Advanced Encryption Standard and has a block size of 128 bits. The cipher was not selected as a finalist. Bluetooth
    Bluetooth

    Bluetooth is a wireless protocol for exchanging data over short distances from fixed and mobile devices, creating personal area networks . It was originally conceived as a wireless alternative to RS232 data cables....
     uses custom algorithms based on SAFER+ for key derivation (called E21 and E22) and authentication as message authentication code
    Message authentication code

    A cryptography message authentication code is a short piece of information used to authenticate a message.A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC ....
    s (called E1). Encryption in Bluetooth does not use SAFER+.
  • SAFER++ (Massey et al, 2000) was submitted to the NESSIE
    NESSIE

    NESSIE was a European research project funded from 2000–2003 to identify secure cryptography Cryptographic primitive....
     project in two versions, one with 64 bits, and the other with 128 bits.


See also

  • Substitution-permutation network
    Substitution-permutation network

    In cryptography, an SP-network, or substitution-permutation network , is a series of linked mathematical operations used in block cipher algorithms such as Advanced Encryption Standard....
  • Confusion and diffusion
    Confusion and diffusion

    In cryptography, confusion and diffusion are two properties of the operation of a secure cipher which were identified by Claude Elwood Shannon in his paper, "Communication Theory of Secrecy Systems" published in 1949....


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