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cryb-to/lib/rsaref/r_dh.c
Dag-Erling Smørgrav ae99587ba4 initial code drop
2014-07-04 11:18:53 +00:00

145 lines
4.8 KiB
C

/* R_DH.C - Diffie-Hellman routines for RSAREF
*/
/* Copyright (C) RSA Laboratories, a division of RSA Data Security,
Inc., created 1993. All rights reserved.
*/
#include "global.h"
#include "rsaref.h"
#include "r_random.h"
#include "nn.h"
#include "prime.h"
/* Generates Diffie-Hellman parameters.
*/
int R_GenerateDHParams (params, primeBits, subPrimeBits, randomStruct)
R_DH_PARAMS *params; /* new Diffie-Hellman parameters */
unsigned int primeBits; /* length of prime in bits */
unsigned int subPrimeBits; /* length of subprime in bits */
R_RANDOM_STRUCT *randomStruct; /* random structure */
{
int status;
NN_DIGIT g[MAX_NN_DIGITS], p[MAX_NN_DIGITS], q[MAX_NN_DIGITS],
t[MAX_NN_DIGITS], u[MAX_NN_DIGITS], v[MAX_NN_DIGITS];
unsigned int pDigits;
pDigits = (primeBits + NN_DIGIT_BITS - 1) / NN_DIGIT_BITS;
/* Generate subprime q between 2^(subPrimeBits-1) and
2^subPrimeBits-1, searching in steps of 2.
*/
NN_Assign2Exp (t, subPrimeBits-1, pDigits);
NN_Assign (u, t, pDigits);
NN_ASSIGN_DIGIT (v, 1, pDigits);
NN_Sub (v, t, v, pDigits);
NN_Add (u, u, v, pDigits);
NN_ASSIGN_DIGIT (v, 2, pDigits);
if ((status = GeneratePrime (q, t, u, v, pDigits, randomStruct)))
return (status);
/* Generate prime p between 2^(primeBits-1) and 2^primeBits-1,
searching in steps of 2*q.
*/
NN_Assign2Exp (t, primeBits-1, pDigits);
NN_Assign (u, t, pDigits);
NN_ASSIGN_DIGIT (v, 1, pDigits);
NN_Sub (v, t, v, pDigits);
NN_Add (u, u, v, pDigits);
NN_LShift (v, q, 1, pDigits);
if ((status = GeneratePrime (p, t, u, v, pDigits, randomStruct)))
return (status);
/* Generate generator g for subgroup as 2^((p-1)/q) mod p.
*/
NN_ASSIGN_DIGIT (g, 2, pDigits);
NN_Div (t, u, p, pDigits, q, pDigits);
NN_ModExp (g, g, t, pDigits, p, pDigits);
params->generatorLen = params->primeLen = DH_PRIME_LEN (primeBits);
NN_Encode (params->prime, params->primeLen, p, pDigits);
NN_Encode (params->generator, params->generatorLen, g, pDigits);
return (0);
}
/* Sets up Diffie-Hellman key agreement. Public value has same length
as prime.
*/
int R_SetupDHAgreement
(publicValue, privateValue, privateValueLen, params, randomStruct)
unsigned char *publicValue; /* new public value */
unsigned char *privateValue; /* new private value */
unsigned int privateValueLen; /* length of private value */
R_DH_PARAMS *params; /* Diffie-Hellman parameters */
R_RANDOM_STRUCT *randomStruct; /* random structure */
{
int status;
NN_DIGIT g[MAX_NN_DIGITS], p[MAX_NN_DIGITS], x[MAX_NN_DIGITS],
y[MAX_NN_DIGITS];
unsigned int pDigits, xDigits;
NN_Decode (p, MAX_NN_DIGITS, params->prime, params->primeLen);
pDigits = NN_Digits (p, MAX_NN_DIGITS);
NN_Decode (g, pDigits, params->generator, params->generatorLen);
/* Generate private value.
*/
if ((status = R_GenerateBytes (privateValue, privateValueLen, randomStruct)))
return (status);
NN_Decode (x, pDigits, privateValue, privateValueLen);
xDigits = NN_Digits (x, pDigits);
/* Compute y = g^x mod p.
*/
NN_ModExp (y, g, x, xDigits, p, pDigits);
NN_Encode (publicValue, params->primeLen, y, pDigits);
/* Zeroize sensitive information.
*/
R_memset ((POINTER)x, 0, sizeof (x));
return (0);
}
/* Computes agreed key from the other party's public value, a private
value, and Diffie-Hellman parameters. Other public value and
agreed-upon key have same length as prime.
Requires otherPublicValue < prime.
*/
int R_ComputeDHAgreedKey
(agreedKey, otherPublicValue, privateValue, privateValueLen, params)
unsigned char *agreedKey; /* new agreed key */
unsigned char *otherPublicValue; /* other's public value */
unsigned char *privateValue; /* private value */
unsigned int privateValueLen; /* length of private value */
R_DH_PARAMS *params; /* Diffie-Hellman parameters */
{
NN_DIGIT p[MAX_NN_DIGITS], x[MAX_NN_DIGITS], y[MAX_NN_DIGITS],
z[MAX_NN_DIGITS];
unsigned int pDigits, xDigits;
NN_Decode (p, MAX_NN_DIGITS, params->prime, params->primeLen);
pDigits = NN_Digits (p, MAX_NN_DIGITS);
NN_Decode (x, pDigits, privateValue, privateValueLen);
xDigits = NN_Digits (x, pDigits);
NN_Decode (y, pDigits, otherPublicValue, params->primeLen);
if (NN_Cmp (y, p, pDigits) >= 0)
return (RE_DATA);
/* Compute z = y^x mod p.
*/
NN_ModExp (z, y, x, xDigits, p, pDigits);
NN_Encode (agreedKey, params->primeLen, z, pDigits);
/* Zeroize sensitive information.
*/
R_memset ((POINTER)x, 0, sizeof (x));
R_memset ((POINTER)z, 0, sizeof (z));
return (0);
}