Oryx (cipher)

ORYX is a stream encryption algorithm with a key length of 96 bits (the export version of the cipher used only 32 bits of the key). Used to protect data in cellular networks such as IS-136 and CDMA2000 . Due to design errors, he used only a 16-bit key. So, having learned the first 25-27 bytes of any data, you can crack it in $2^{16}$ ${\ displaystyle 2 ^ {16}}$ $2 ^ {16}$ operations. ^[one]

Content

Algorithm Description

The ORYX cipher consists of four components: three 32-bit RSLOS , which are designated as LFSR _A , LFSR _B and LFSR _K , an S-box containing known permutations of P (values from 0 to 255).

Feedback Functions for LFSR _K

$x^{32}+x^{28}+x^{19}+x^{18}+x^{16}+x^{14}+x^{11}+x^{10}+x^{9}+x^{6}+x^{5}+x+1$ ${\ displaystyle x ^ {32} + x ^ {28} + x ^ {19} + x ^ {18} + x ^ {16} + x ^ {14} + x ^ {11} + x ^ {10} + x ^ {9} + x ^ {6} + x ^ {5} + x + 1}$

The feedback functions for LFSR _{A are} defined as

$x^{32}+x^{26}+x^{23}+x^{22}+x^{16}+x^{12}+x^{11}+x^{10}+x^{8}+x^{7}+x^{5}+x^{4}+x^{2}+x+1$ ${\ displaystyle x ^ {32} + x ^ {26} + x ^ {23} + x ^ {22} + x ^ {16} + x ^ {12} + x ^ {11} + x ^ {10} + x ^ {8} + x ^ {7} + x ^ {5} + x ^ {4} + x ^ {2} + x + 1}$

and

$x^{32}+x^{27}+x^{26}+x^{25}+x^{24}+x^{23}+x^{22}+x^{17}+x^{13}+x^{11}+x^{10}+x^{9}+x^{8}+x^{7}+x^{2}+x+1$ ${\ displaystyle x ^ {32} + x ^ {27} + x ^ {26} + x ^ {25} + x ^ {24} + x ^ {23} + x ^ {22} + x ^ {17} + x ^ {13} + x ^ {11} + x ^ {10} + x ^ {9} + x ^ {8} + x ^ {7} + x ^ {2} + x + 1}$

Feedback Functions for LFSR _B

$x^{32}+x^{31}+x^{21}+x^{20}+x^{16}+x^{15}+x^{6}+x^{3}+x+1$ ${\ displaystyle x ^ {32} + x ^ {31} + x ^ {21} + x ^ {20} + x ^ {16} + x ^ {15} + x ^ {6} + x ^ {3} + x + 1}$

Work algorithm:

LFSR _K runs once.
LFSR _A operates once, with one of the polynomials depending on the state of LFSR _K.
LFSR _B runs once or twice, depending on the state of LFSR _K.
High bytes in LFSR _A , LFSR _B, and LFSR _{K are} combined into Keystream bytes:

Keystream = {High8K + L [High8A] + L [High8B]} mod 256

Notes

↑ [D. Wagner, L. Simpson, E. Dawson, J. Kelsey, W. Millan, and B. Schneier http://www.schneier.com/paper-oryx.pdf “Cryptanalysis of ORYX”], Fifth Annual Workshop on Selected Areas in Cryptography, Springer Verlag, August 1998, to appear.

Links

[1] [D. Wagner, L. Simpson, E. Dawson, J. Kelsey, W. Millan, and B. Schneier http://www.schneier.com/paper-oryx.pdf “Cryptanalysis of ORYX”], Fifth Annual Workshop on Selected Areas in Cryptography, Springer Verlag, August 1998, to appear.

Oryx (cipher)

Content

Algorithm Description

See also

Notes

Links

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