1SCRYPT(7) OpenSSL SCRYPT(7)
2
6 scrypt - EVP_PKEY scrypt KDF support
7
9 The EVP_PKEY_SCRYPT algorithm implements the scrypt password based key
10 derivation function, as described in RFC 7914. It is memory-hard in
11 the sense that it deliberately requires a significant amount of RAM for
12 efficient computation. The intention of this is to render brute forcing
13 of passwords on systems that lack large amounts of main memory (such as
14 GPUs or ASICs) computationally infeasible.
15 scrypt provides three work factors that can be customized: N, r and p.
17 N, which has to be a positive power of two, is the general work factor
18 and scales CPU time in an approximately linear fashion. r is the block
19 size of the internally used hash function and p is the parallelization
20 factor. Both r and p need to be greater than zero. The amount of RAM
21 that scrypt requires for its computation is roughly (128 * N * r * p)
22 bytes.
23 In the original paper of Colin Percival ("Stronger Key Derivation via
25 Sequential Memory-Hard Functions", 2009), the suggested values that
26 give a computation time of less than 5 seconds on a 2.5 GHz Intel Core
27 2 Duo are N = 2^20 = 1048576, r = 8, p = 1. Consequently, the required
28 amount of memory for this computation is roughly 1 GiB. On a more
29 recent CPU (Intel i7-5930K at 3.5 GHz), this computation takes about 3
30 seconds. When N, r or p are not specified, they default to 1048576, 8,
31 and 1, respectively. The default amount of RAM that may be used by
32 scrypt defaults to 1025 MiB.
33
35 A context for scrypt can be obtained by calling:
36 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SCRYPT, NULL);
38 The output length of an scrypt key derivation is specified via the
40 length parameter to the EVP_PKEY_derive(3) function.
41
43 This example derives a 64-byte long test vector using scrypt using the
44 password "password", salt "NaCl" and N = 1024, r = 8, p = 16.
45 EVP_PKEY_CTX *pctx;
47 unsigned char out[64];
48 size_t outlen = sizeof(out);
50 pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SCRYPT, NULL);
51 if (EVP_PKEY_derive_init(pctx) <= 0) {
53 error("EVP_PKEY_derive_init");
54 }
55 if (EVP_PKEY_CTX_set1_pbe_pass(pctx, "password", 8) <= 0) {
56 error("EVP_PKEY_CTX_set1_pbe_pass");
57 }
58 if (EVP_PKEY_CTX_set1_scrypt_salt(pctx, "NaCl", 4) <= 0) {
59 error("EVP_PKEY_CTX_set1_scrypt_salt");
60 }
61 if (EVP_PKEY_CTX_set_scrypt_N(pctx, 1024) <= 0) {
62 error("EVP_PKEY_CTX_set_scrypt_N");
63 }
64 if (EVP_PKEY_CTX_set_scrypt_r(pctx, 8) <= 0) {
65 error("EVP_PKEY_CTX_set_scrypt_r");
66 }
67 if (EVP_PKEY_CTX_set_scrypt_p(pctx, 16) <= 0) {
68 error("EVP_PKEY_CTX_set_scrypt_p");
69 }
70 if (EVP_PKEY_derive(pctx, out, &outlen) <= 0) {
71 error("EVP_PKEY_derive");
72 }
73 {
75 const unsigned char expected[sizeof(out)] = {
76 0xfd, 0xba, 0xbe, 0x1c, 0x9d, 0x34, 0x72, 0x00,
77 0x78, 0x56, 0xe7, 0x19, 0x0d, 0x01, 0xe9, 0xfe,
78 0x7c, 0x6a, 0xd7, 0xcb, 0xc8, 0x23, 0x78, 0x30,
79 0xe7, 0x73, 0x76, 0x63, 0x4b, 0x37, 0x31, 0x62,
80 0x2e, 0xaf, 0x30, 0xd9, 0x2e, 0x22, 0xa3, 0x88,
81 0x6f, 0xf1, 0x09, 0x27, 0x9d, 0x98, 0x30, 0xda,
82 0xc7, 0x27, 0xaf, 0xb9, 0x4a, 0x83, 0xee, 0x6d,
83 0x83, 0x60, 0xcb, 0xdf, 0xa2, 0xcc, 0x06, 0x40
84 };
85 assert(!memcmp(out, expected, sizeof(out)));
87 }
88 EVP_PKEY_CTX_free(pctx);
90
92 RFC 7914
93
95 EVP_PKEY_CTX_set1_scrypt_salt(3), EVP_PKEY_CTX_set_scrypt_N(3),
96 EVP_PKEY_CTX_set_scrypt_r(3), EVP_PKEY_CTX_set_scrypt_p(3),
97 EVP_PKEY_CTX_set_scrypt_maxmem_bytes(3), EVP_PKEY_CTX_new(3),
98 EVP_PKEY_CTX_ctrl_str(3), EVP_PKEY_derive(3)
99
101 Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.
102 Licensed under the OpenSSL license (the "License"). You may not use
104 this file except in compliance with the License. You can obtain a copy
105 in the file LICENSE in the source distribution or at
106 <https://www.openssl.org/source/license.html>.
1071.1.1l 2021-09-15 SCRYPT(7)