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1.1 root 1: /* R_DH.C - Diffie-Hellman routines for RSAREF
2: */
3:
4: /* Copyright (C) RSA Laboratories, a division of RSA Data Security,
5: Inc., created 1993. All rights reserved.
6: */
7:
8: #include "global.h"
9: #include "rsaref.h"
10: #include "r_random.h"
11: #include "nn.h"
12: #include "prime.h"
13:
14: /* Generates Diffie-Hellman parameters.
15: */
16: int R_GenerateDHParams (params, primeBits, subPrimeBits, randomStruct)
17: R_DH_PARAMS *params; /* new Diffie-Hellman parameters */
18: unsigned int primeBits; /* length of prime in bits */
19: unsigned int subPrimeBits; /* length of subprime in bits */
20: R_RANDOM_STRUCT *randomStruct; /* random structure */
21: {
22: int status;
23: NN_DIGIT g[MAX_NN_DIGITS], p[MAX_NN_DIGITS], q[MAX_NN_DIGITS],
24: t[MAX_NN_DIGITS], u[MAX_NN_DIGITS], v[MAX_NN_DIGITS];
25: unsigned int pDigits;
26:
27: pDigits = (primeBits + NN_DIGIT_BITS - 1) / NN_DIGIT_BITS;
28:
29: /* Generate subprime q between 2^(subPrimeBits-1) and
30: 2^subPrimeBits-1, searching in steps of 2.
31: */
32: NN_Assign2Exp (t, subPrimeBits-1, pDigits);
33: NN_Assign (u, t, pDigits);
34: NN_ASSIGN_DIGIT (v, 1, pDigits);
35: NN_Sub (v, t, v, pDigits);
36: NN_Add (u, u, v, pDigits);
37: NN_ASSIGN_DIGIT (v, 2, pDigits);
38: if (status = GeneratePrime (q, t, u, v, pDigits, randomStruct))
39: return (status);
40:
41: /* Generate prime p between 2^(primeBits-1) and 2^primeBits-1,
42: searching in steps of 2*q.
43: */
44: NN_Assign2Exp (t, primeBits-1, pDigits);
45: NN_Assign (u, t, pDigits);
46: NN_ASSIGN_DIGIT (v, 1, pDigits);
47: NN_Sub (v, t, v, pDigits);
48: NN_Add (u, u, v, pDigits);
49: NN_LShift (v, q, 1, pDigits);
50: if (status = GeneratePrime (p, t, u, v, pDigits, randomStruct))
51: return (status);
52:
53: /* Generate generator g for subgroup as 2^((p-1)/q) mod p.
54: */
55: NN_ASSIGN_DIGIT (g, 2, pDigits);
56: NN_Div (t, u, p, pDigits, q, pDigits);
57: NN_ModExp (g, g, t, pDigits, p, pDigits);
58:
59: params->generatorLen = params->primeLen = DH_PRIME_LEN (primeBits);
60: NN_Encode (params->prime, params->primeLen, p, pDigits);
61: NN_Encode (params->generator, params->generatorLen, g, pDigits);
62:
63: return (0);
64: }
65:
66: /* Sets up Diffie-Hellman key agreement. Public value has same length
67: as prime.
68: */
69: int R_SetupDHAgreement
70: (publicValue, privateValue, privateValueLen, params, randomStruct)
71: unsigned char *publicValue; /* new public value */
72: unsigned char *privateValue; /* new private value */
73: unsigned int privateValueLen; /* length of private value */
74: R_DH_PARAMS *params; /* Diffie-Hellman parameters */
75: R_RANDOM_STRUCT *randomStruct; /* random structure */
76: {
77: int status;
78: NN_DIGIT g[MAX_NN_DIGITS], p[MAX_NN_DIGITS], x[MAX_NN_DIGITS],
79: y[MAX_NN_DIGITS];
80: unsigned int pDigits, xDigits;
81:
82: NN_Decode (p, MAX_NN_DIGITS, params->prime, params->primeLen);
83: pDigits = NN_Digits (p, MAX_NN_DIGITS);
84: NN_Decode (g, pDigits, params->generator, params->generatorLen);
85:
86: /* Generate private value.
87: */
88: if (status = R_GenerateBytes (privateValue, privateValueLen, randomStruct))
89: return (status);
90: NN_Decode (x, pDigits, privateValue, privateValueLen);
91: xDigits = NN_Digits (x, pDigits);
92:
93: /* Compute y = g^x mod p.
94: */
95: NN_ModExp (y, g, x, xDigits, p, pDigits);
96:
97: NN_Encode (publicValue, params->primeLen, y, pDigits);
98:
99: /* Zeroize sensitive information.
100: */
101: R_memset ((POINTER)x, 0, sizeof (x));
102:
103: return (0);
104: }
105:
106: /* Computes agreed key from the other party's public value, a private
107: value, and Diffie-Hellman parameters. Other public value and
108: agreed-upon key have same length as prime.
109:
110: Requires otherPublicValue < prime.
111: */
112: int R_ComputeDHAgreedKey
113: (agreedKey, otherPublicValue, privateValue, privateValueLen, params)
114: unsigned char *agreedKey; /* new agreed key */
115: unsigned char *otherPublicValue; /* other's public value */
116: unsigned char *privateValue; /* private value */
117: unsigned int privateValueLen; /* length of private value */
118: R_DH_PARAMS *params; /* Diffie-Hellman parameters */
119: {
120: NN_DIGIT p[MAX_NN_DIGITS], x[MAX_NN_DIGITS], y[MAX_NN_DIGITS],
121: z[MAX_NN_DIGITS];
122: unsigned int pDigits, xDigits;
123:
124: NN_Decode (p, MAX_NN_DIGITS, params->prime, params->primeLen);
125: pDigits = NN_Digits (p, MAX_NN_DIGITS);
126: NN_Decode (x, pDigits, privateValue, privateValueLen);
127: xDigits = NN_Digits (x, pDigits);
128: NN_Decode (y, pDigits, otherPublicValue, params->primeLen);
129:
130: if (NN_Cmp (y, p, pDigits) >= 0)
131: return (RE_DATA);
132:
133: /* Compute z = y^x mod p.
134: */
135: NN_ModExp (z, y, x, xDigits, p, pDigits);
136:
137: NN_Encode (agreedKey, params->primeLen, z, pDigits);
138:
139: /* Zeroize sensitive information.
140: */
141: R_memset ((POINTER)x, 0, sizeof (x));
142: R_memset ((POINTER)z, 0, sizeof (z));
143:
144: return (0);
145: }
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