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[求助]Related-Key Cryptanalysis of TEA
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2010-4-17 22:14
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TEA, a Tiny Encryption Algorithm
这个应该是David J. Wheeler和Roger M. Needham两个人提出TEA加密的论文吧。 Encode Routine, written in the C language, for encoding with key k[0] - k[3]128bit）. Data in v[0] and v[1]（64bit）. void code(long* v, long* k) { unsigned long y=v[O] ,z=v[l], sum=O, /* set up */ delta=Ox9e3779b9, /* a key schedule constant */ n=32 ; while (n-->O) { /* basic cycle start */ sum += delta ; y += ((z<<4)+k[0]) ^ (z+sum) ^ ((z>>5)+k[1]) ; z += ((y<<4)+k[2]) ^ (y+sum) ^ ((y>>5)+k[3]) ; } /* end cycle */ v[O]=y ; v[1]=z ; } Decode Routine void decode(long* v,long* k) unsigned long n=32, sum, y=v[O], z=v[l], delta=0x9e3779b9 ; sum=delta<<S ; /* start cycle */ while (n-->0) { z-= ((y<<4)+k[2]) ^ (y+sum) ^ ((y>>S)+k[3]) ; y-= ((z<<4)+k[0]) ^ (z+sum) ^ ((z>>S)+k[1]) ; sure-:delta ; } /* end cycle */ v[0]:y ; v[1]=z ; } 其中delta = （（5^0.5）-1）*2^31 = 0x9e3779b9 Basics of the routine It is a Feistel type routine although addition and subtraction are used as the reversible operators rather than XOR. The routine relies on the alternate use of XOR and ADD to provide nonlinearity. A dual shift causes all bits of the key and data to be mixed repeatedly. The number of rounds before a single bit change of the data or key has spread very close to 32 is at most six, so that sixteen cycles may suffice and we suggest 32. The key is set at 128 bits as this is enough to prevent simple search techniques being effective. This type of algorithm can replace DES in software, and is short enough to write into almost any program on any computer.感觉作者当时想用这个取代DES 
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