411 lines
10 KiB
C
411 lines
10 KiB
C
/*
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* idea.c - C source code for IDEA block cipher.
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* IDEA (International Data Encryption Algorithm), formerly known as
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* IPES (Improved Proposed Encryption Standard).
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* Algorithm developed by Xuejia Lai and James L. Massey, of ETH Zurich.
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* This implementation modified and derived from original C code
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* developed by Xuejia Lai.
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* Zero-based indexing added, names changed from IPES to IDEA.
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* CFB functions added. Random number routines added.
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*
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* Extensively optimized and restructured by Colin Plumb.
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*
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* There are two adjustments that can be made to this code to
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* speed it up. Defaults may be used for PCs. Only the -DIDEA32
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* pays off significantly if selectively set or not set.
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* Experiment to see what works best for your machine.
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*
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* Multiplication: default is inline, -DAVOID_JUMPS uses a
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* different version that does not do any conditional
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* jumps (a few percent worse on a SPARC), while
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* -DSMALL_CACHE takes it out of line to stay
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* within a small on-chip code cache.
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* Variables: normally, 16-bit variables are used, but some
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* machines (notably RISCs) do not have 16-bit registers,
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* so they do a great deal of masking. -DIDEA32 uses "int"
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* register variables and masks explicitly only where
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* necessary. On a SPARC, for example, this boosts
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* performace by 30%.
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*
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* The IDEA(tm) block cipher is covered by patents held by ETH and a
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* Swiss company called Ascom-Tech AG. The Swiss patent number is
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* PCT/CH91/00117, the European patent number is EP 0 482 154 B1, and
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* the U.S. patent number is US005214703. IDEA(tm) is a trademark of
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* Ascom-Tech AG. There is no license fee required for noncommercial
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* use. Commercial users may obtain licensing details from Dieter
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* Profos, Ascom Tech AG, Solothurn Lab, Postfach 151, 4502 Solothurn,
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* Switzerland, Tel +41 65 242885, Fax +41 65 235761.
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*
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* The IDEA block cipher uses a 64-bit block size, and a 128-bit key
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* size. It breaks the 64-bit cipher block into four 16-bit words
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* because all of the primitive inner operations are done with 16-bit
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* arithmetic. It likewise breaks the 128-bit cipher key into eight
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* 16-bit words.
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*
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* For further information on the IDEA cipher, see the book:
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* Xuejia Lai, "On the Design and Security of Block Ciphers",
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* ETH Series on Information Processing (ed. J.L. Massey) Vol 1,
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* Hartung-Gorre Verlag, Konstanz, Switzerland, 1992. ISBN
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* 3-89191-573-X.
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*
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* This code runs on arrays of bytes by taking pairs in big-endian
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* order to make the 16-bit words that IDEA uses internally. This
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* produces the same result regardless of the byte order of the
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* native CPU.
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*/
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#include <string.h>
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#ifdef _MSC_VER
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#include "../crypt.h"
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#include "idea.h"
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#else
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#include "crypt.h"
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#include "idea/idea.h"
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#endif /* _MSC_VER */
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#ifdef BIG_ENDIAN /* This code uses slightly different names */
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#define HIGHFIRST
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#endif /* BIG_ENDIAN */
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#ifdef IDEA32 /* Use >16-bit temporaries */
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#define low16(x) ((x) & 0xFFFF)
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typedef unsigned int uint16; /* at LEAST 16 bits, maybe more */
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#else
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#define low16(x) (x) /* this is only ever applied to uint16's */
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typedef word16 uint16;
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#endif
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#ifdef _GNUC_
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/* __const__ simply means there are no side effects for this function,
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* which is useful info for the gcc optimizer
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*/
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#define CONST __const__
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#else
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#define CONST
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#endif
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/*
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* Multiplication, modulo (2**16)+1
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* Note that this code is structured on the assumption that
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* untaken branches are cheaper than taken branches, and the
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* compiler doesn't schedule branches.
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*/
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#ifdef SMALL_CACHE
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CONST static uint16
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mul(register uint16 a, register uint16 b)
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{
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register word32 p;
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p = (word32)a * b;
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if (p) {
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b = low16(p);
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a = p>>16;
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return (b - a) + (b < a);
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} else if (a) {
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return 1-b;
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} else {
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return 1-a;
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}
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} /* mul */
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#endif /* SMALL_CACHE */
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/*
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* Compute the multiplicative inverse of x, modulo 65537, using Euclid's
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* algorithm. It is unrolled twice to avoid swapping the registers each
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* iteration, and some subtracts of t have been changed to adds.
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*/
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CONST static uint16
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mulInv(uint16 x)
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{
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uint16 t0, t1;
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uint16 q, y;
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if (x <= 1)
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return x; /* 0 and 1 are self-inverse */
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t1 = 0x10001L / x; /* Since x >= 2, this fits into 16 bits */
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y = 0x10001L % x;
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if (y == 1)
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return ( uint16 ) low16(1-t1);
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t0 = 1;
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do {
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q = x / y;
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x = x % y;
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t0 += q * t1;
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if (x == 1)
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return t0;
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q = y / x;
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y = y % x;
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t1 += q * t0;
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} while (y != 1);
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return ( uint16 ) low16(1-t1);
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} /* mukInv */
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/*
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* Expand a 128-bit user key to a working encryption key EK
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*/
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void
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ideaExpandKey(byte const *userkey, word16 *EK)
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{
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int i,j;
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for (j=0; j<8; j++) {
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EK[j] = (userkey[0]<<8) + userkey[1];
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userkey += 2;
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}
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for (i=0; j < IDEAKEYLEN; j++) {
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i++;
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EK[i+7] = (EK[i & 7] << 9) | (EK[i+1 & 7] >> 7);
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EK += i & 8;
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i &= 7;
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}
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} /* ideaExpandKey */
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/*
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* Compute IDEA decryption key DK from an expanded IDEA encryption key EK
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* Note that the input and output may be the same. Thus, the key is
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* inverted into an internal buffer, and then copied to the output.
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*/
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void
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#ifdef _DCC
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ideaInvertKey(word16 *EK, word16 DK[IDEAKEYLEN])
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#else
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ideaInvertKey(word16 const *EK, word16 DK[IDEAKEYLEN])
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#endif
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{
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int i;
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uint16 t1, t2, t3;
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word16 temp[IDEAKEYLEN];
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word16 *p = temp + IDEAKEYLEN;
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t1 = mulInv(*EK++);
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t2 = - ( int ) *EK++;
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t3 = - ( int ) *EK++;
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*--p = mulInv(*EK++);
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*--p = t3;
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*--p = t2;
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*--p = t1;
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for (i = 0; i < IDEAROUNDS-1; i++) {
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t1 = *EK++;
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*--p = *EK++;
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*--p = t1;
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t1 = mulInv(*EK++);
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t2 = - ( int ) *EK++;
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t3 = - ( int ) *EK++;
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*--p = mulInv(*EK++);
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*--p = t2;
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*--p = t3;
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*--p = t1;
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}
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t1 = *EK++;
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*--p = *EK++;
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*--p = t1;
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t1 = mulInv(*EK++);
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t2 = - ( int ) *EK++;
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t3 = - ( int ) *EK++;
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*--p = mulInv(*EK++);
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*--p = t3;
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*--p = t2;
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*--p = t1;
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/* Copy and destroy temp copy */
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memcpy(DK, temp, sizeof(temp));
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burn(temp);
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} /* ideaInvertKey */
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/*
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* MUL(x,y) computes x = x*y, modulo 0x10001. Requires two temps,
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* t16 and t32. x is modified, and must me a side-effect-free lvalue.
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* y may be anything, but unlike x, must be strictly 16 bits even if
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* low16() is #defined.
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* All of these are equivalent - see which is faster on your machine
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*/
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#ifdef SMALL_CACHE
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#define MUL(x,y) (x = mul(low16(x),y))
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#else /* !SMALL_CACHE */
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#ifdef AVOID_JUMPS
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#define MUL(x,y) (x = low16(x-1), t16 = low16((y)-1), \
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t32 = (word32)x*t16 + x + t16 + 1, x = low16(t32), \
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t16 = t32>>16, x = (x-t16) + (x<t16) )
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#else /* !AVOID_JUMPS (default) */
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#define MUL(x,y) \
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((t16 = (y)) ? \
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(x=low16(x)) ? \
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t32 = (word32)x*t16, \
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x = low16(t32), \
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t16 = t32>>16, \
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x = (x-t16)+(x<t16) \
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: \
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(x = 1-t16) \
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: \
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(x = 1-x))
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#endif
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#endif
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/* IDEA encryption/decryption algorithm */
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/* Note that in and out can be the same buffer */
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void
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#ifdef _DCC
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ideaCipher(byte (inbuf[8]), byte (outbuf[8]), word16 *key)
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#else
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ideaCipher(byte const (inbuf[8]), byte (outbuf[8]), word16 const *key)
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#endif
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{
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register uint16 x1, x2, x3, x4, s2, s3;
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word16 *in, *out;
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#ifndef SMALL_CACHE
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register uint16 t16; /* Temporaries needed by MUL macro */
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register word32 t32;
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#endif
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int r = IDEAROUNDS;
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in = (word16 *)inbuf;
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x1 = *in++; x2 = *in++;
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x3 = *in++; x4 = *in;
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#ifndef HIGHFIRST
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x1 = (x1>>8) | (x1<<8);
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x2 = (x2>>8) | (x2<<8);
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x3 = (x3>>8) | (x3<<8);
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x4 = (x4>>8) | (x4<<8);
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#endif
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do {
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MUL(x1,*key++);
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x2 += *key++;
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x3 += *key++;
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MUL(x4, *key++);
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s3 = x3;
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x3 ^= x1;
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MUL(x3, *key++);
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s2 = x2;
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x2 ^= x4;
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x2 += x3;
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MUL(x2, *key++);
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x3 += x2;
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x1 ^= x2; x4 ^= x3;
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x2 ^= s3; x3 ^= s2;
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} while (--r);
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MUL(x1, *key++);
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x3 += *key++;
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x2 += *key++;
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MUL(x4, *key);
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out = (word16 *)outbuf;
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#ifdef HIGHFIRST
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*out++ = x1;
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*out++ = x3;
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*out++ = x2;
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*out = x4;
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#else /* !HIGHFIRST */
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x1 = low16(x1);
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x2 = low16(x2);
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x3 = low16(x3);
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x4 = low16(x4);
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*out++ = (x1>>8) | (x1<<8);
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*out++ = (x3>>8) | (x3<<8);
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*out++ = (x2>>8) | (x2<<8);
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*out = (x4>>8) | (x4<<8);
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#endif
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} /* ideaCipher */
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/*-------------------------------------------------------------*/
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#ifdef TEST
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#include <stdio.h>
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#include <time.h>
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/*
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* This is the number of Kbytes of test data to encrypt.
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* It defaults to 1 MByte.
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*/
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#ifndef BLOCKS
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#ifndef KBYTES
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#define KBYTES 1024
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#endif
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#define BLOCKS (64*KBYTES)
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#endif
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int
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main(void)
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{ /* Test driver for IDEA cipher */
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int i, j, k;
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byte userkey[16];
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word16 EK[IDEAKEYLEN], DK[IDEAKEYLEN];
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byte XX[8], YY[8], ZZ[8];
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clock_t start, end;
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long l;
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/* Make a sample user key for testing... */
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for(i=0; i<16; i++)
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userkey[i] = i+1;
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/* Compute encryption subkeys from user key... */
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ideaExpandKey(userkey, EK);
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printf("\nEncryption key subblocks: ");
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for (j=0; j<IDEAROUNDS+1; j++) {
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printf("\nround %d: ", j+1);
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if (j < IDEAROUNDS)
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for(i=0; i<6; i++)
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printf(" %6u", EK[j*6+i]);
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else
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for(i=0; i<4; i++)
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printf(" %6u", EK[j*6+i]);
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}
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/* Compute decryption subkeys from encryption subkeys... */
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ideaInvertKey(EK, DK);
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printf("\nDecryption key subblocks: ");
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for (j=0; j<IDEAROUNDS+1; j++) {
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printf("\nround %d: ", j+1);
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if (j < IDEAROUNDS)
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for(i=0; i<6; i++)
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printf(" %6u", DK[j*6+i]);
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else
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for(i=0; i<4; i++)
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printf(" %6u", DK[j*6+i]);
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}
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/* Make a sample plaintext pattern for testing... */
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for (k=0; k<8; k++)
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XX[k] = k;
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printf("\n Encrypting %d bytes (%ld blocks)...", BLOCKS*16, BLOCKS);
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fflush(stdout);
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start = clock();
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memcpy(YY, XX, 8);
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for (l = 0; l < BLOCKS; l++)
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ideaCipher(YY, YY, EK); /* repeated encryption */
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memcpy(ZZ, YY, 8);
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for (l = 0; l < BLOCKS; l++)
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ideaCipher(ZZ, ZZ, DK); /* repeated decryption */
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end = clock() - start;
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l = end / (CLOCKS_PER_SEC/1000) + 1;
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i = l/1000;
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j = l%1000;
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l = (16 * BLOCKS * (CLOCKS_PER_SEC/1000)) / (end/1000);
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printf("%d.%03d seconds = %ld bytes per second\n", i, j, l);
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printf("\nX %3u %3u %3u %3u %3u %3u %3u %3u\n",
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XX[0], XX[1], XX[2], XX[3], XX[4], XX[5], XX[6], XX[7]);
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printf("\nY %3u %3u %3u %3u %3u %3u %3u %3u\n",
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YY[0], YY[1], YY[2], YY[3], YY[4], YY[5], YY[6], YY[7]);
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printf("\nZ %3u %3u %3u %3u %3u %3u %3u %3u\n",
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ZZ[0], ZZ[1], ZZ[2], ZZ[3], ZZ[4], ZZ[5], ZZ[6], ZZ[7]);
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/* Now decrypted ZZ should be same as original XX */
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for (k=0; k<8; k++)
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if (XX[k] != ZZ[k]) {
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printf("\n\07Error! Noninvertable encryption.\n");
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exit(-1); /* error exit */
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}
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printf("\nNormal exit.\n");
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return 0; /* normal exit */
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} /* main */
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#endif /* TEST */
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/* end of idea.c */
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