EVP_KDF_SCRYPT(7ssl)

1EVP_KDF_SCRYPT(7)                   OpenSSL                  EVP_KDF_SCRYPT(7)
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NAME

6       EVP_KDF_SCRYPT - The scrypt EVP_KDF implementation
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DESCRIPTION

9       Support for computing the scrypt password-based KDF through the EVP_KDF
10       API.
11
12       The EVP_KDF_SCRYPT algorithm implements the scrypt password-based key
13       derivation function, as described in RFC 7914.  It is memory-hard in
14       the sense that it deliberately requires a significant amount of RAM for
15       efficient computation. The intention of this is to render brute forcing
16       of passwords on systems that lack large amounts of main memory (such as
17       GPUs or ASICs) computationally infeasible.
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19       scrypt provides three work factors that can be customized: N, r and p.
20       N, which has to be a positive power of two, is the general work factor
21       and scales CPU time in an approximately linear fashion. r is the block
22       size of the internally used hash function and p is the parallelization
23       factor. Both r and p need to be greater than zero. The amount of RAM
24       that scrypt requires for its computation is roughly (128 * N * r * p)
25       bytes.
26
27       In the original paper of Colin Percival ("Stronger Key Derivation via
28       Sequential Memory-Hard Functions", 2009), the suggested values that
29       give a computation time of less than 5 seconds on a 2.5 GHz Intel Core
30       2 Duo are N = 2^20 = 1048576, r = 8, p = 1. Consequently, the required
31       amount of memory for this computation is roughly 1 GiB. On a more
32       recent CPU (Intel i7-5930K at 3.5 GHz), this computation takes about 3
33       seconds. When N, r or p are not specified, they default to 1048576, 8,
34       and 1, respectively. The maximum amount of RAM that may be used by
35       scrypt defaults to 1025 MiB.
36
37   Numeric identity
38       EVP_KDF_SCRYPT is the numeric identity for this implementation; it can
39       be used with the EVP_KDF_CTX_new_id() function.
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41   Supported controls
42       The supported controls are:
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44       EVP_KDF_CTRL_SET_PASS
45       EVP_KDF_CTRL_SET_SALT
46           These controls work as described in "CONTROLS" in EVP_KDF_CTX(3).
47
48       EVP_KDF_CTRL_SET_SCRYPT_N
49       EVP_KDF_CTRL_SET_SCRYPT_R
50       EVP_KDF_CTRL_SET_SCRYPT_P
51           EVP_KDF_CTRL_SET_SCRYPT_N expects one argument: "uint64_t N"
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53           EVP_KDF_CTRL_SET_SCRYPT_R expects one argument: "uint32_t r"
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55           EVP_KDF_CTRL_SET_SCRYPT_P expects one argument: "uint32_t p"
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57           These controls configure the scrypt work factors N, r and p.
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59           EVP_KDF_ctrl_str() type strings: "N", "r" and "p", respectively.
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61           The corresponding value strings are expected to be decimal numbers.
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NOTES

64       A context for scrypt can be obtained by calling:
65
66        EVP_KDF_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_SCRYPT);
67
68       The output length of an scrypt key derivation is specified via the
69       keylen parameter to the EVP_KDF_derive(3) function.
70

EXAMPLE

72       This example derives a 64-byte long test vector using scrypt with the
73       password "password", salt "NaCl" and N = 1024, r = 8, p = 16.
74
75        EVP_KDF_CTX *kctx;
76        unsigned char out[64];
77
78        kctx = EVP_KDF_CTX_new_id(EVP_KDF_SCRYPT);
79
80        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_PASS, "password", (size_t)8) <= 0) {
81            error("EVP_KDF_CTRL_SET_PASS");
82        }
83        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SALT, "NaCl", (size_t)4) <= 0) {
84            error("EVP_KDF_CTRL_SET_SALT");
85        }
86        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SCRYPT_N, (uint64_t)1024) <= 0) {
87            error("EVP_KDF_CTRL_SET_SCRYPT_N");
88        }
89        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SCRYPT_R, (uint32_t)8) <= 0) {
90            error("EVP_KDF_CTRL_SET_SCRYPT_R");
91        }
92        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SCRYPT_P, (uint32_t)16) <= 0) {
93            error("EVP_KDF_CTRL_SET_SCRYPT_P");
94        }
95        if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) {
96            error("EVP_KDF_derive");
97        }
98
99        {
100            const unsigned char expected[sizeof(out)] = {
101                0xfd, 0xba, 0xbe, 0x1c, 0x9d, 0x34, 0x72, 0x00,
102                0x78, 0x56, 0xe7, 0x19, 0x0d, 0x01, 0xe9, 0xfe,
103                0x7c, 0x6a, 0xd7, 0xcb, 0xc8, 0x23, 0x78, 0x30,
104                0xe7, 0x73, 0x76, 0x63, 0x4b, 0x37, 0x31, 0x62,
105                0x2e, 0xaf, 0x30, 0xd9, 0x2e, 0x22, 0xa3, 0x88,
106                0x6f, 0xf1, 0x09, 0x27, 0x9d, 0x98, 0x30, 0xda,
107                0xc7, 0x27, 0xaf, 0xb9, 0x4a, 0x83, 0xee, 0x6d,
108                0x83, 0x60, 0xcb, 0xdf, 0xa2, 0xcc, 0x06, 0x40
109            };
110
111            assert(!memcmp(out, expected, sizeof(out)));
112        }
113
114        EVP_KDF_CTX_free(kctx);
115

CONFORMING TO

117       RFC 7914
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COPYRIGHT

124       Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.
125
126       Licensed under the OpenSSL license (the "License").  You may not use
127       this file except in compliance with the License.  You can obtain a copy
128       in the file LICENSE in the source distribution or at
129       <https://www.openssl.org/source/license.html>.
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1331.1.1d                            2019-10-03                 EVP_KDF_SCRYPT(7)

NAME

DESCRIPTION

NOTES

EXAMPLE

CONFORMING TO

SEE ALSO

COPYRIGHT