NAME<\/a> EVP_KDF_SCRYPT \u2212 The scrypt EVP_KDF implementation<\/p>\n Support for computing the scrypt<\/b> password-based KDF<\/small> through the EVP_KDF<\/small><\/b> API.<\/small><\/p>\n The EVP_KDF_SCRYPT<\/small> algorithm implements the scrypt password-based key derivation function, as described in RFC 7914.<\/small> It is memory-hard in the sense that it deliberately requires a significant amount of RAM<\/small> for efficient computation. The intention of this is to render brute forcing of passwords on systems that lack large amounts of main memory (such as GPUs or ASICs) computationally infeasible.<\/p>\n scrypt provides three work factors that can be customized: N, r and p. N, which has to be a positive power of two, is the general work factor and scales CPU<\/small> time in an approximately linear fashion. r is the block size of the internally used hash function and p is the parallelization factor. Both r and p need to be greater than zero. The amount of RAM<\/small> that scrypt requires for its computation is roughly (128 bodies manpages.csv script_extrae_body.sh script.sh usr N bodies manpages.csv script_extrae_body.sh script.sh usr r bodies manpages.csv script_extrae_body.sh script.sh usr p) bytes.<\/p>\n In the original paper of Colin Percival (“Stronger Key Derivation via Sequential Memory-Hard Functions”, 2009), the suggested values that give a computation time of less than 5 seconds on a 2.5 GHz Intel Core 2 Duo are N = 2^20 = 1048576, r = 8, p = 1. Consequently, the required amount of memory for this computation is roughly 1 GiB. On a more recent CPU<\/small> (Intel i7\u22125930K at 3.5 GHz), this computation takes about 3 seconds. When N, r or p are not specified, they default to 1048576, 8, and 1, respectively. The maximum amount of RAM<\/small> that may be used by scrypt defaults to 1025 MiB.<\/p>\n Numeric identity Supported controls<\/b> These controls work as described in ” CONTROLS”<\/small> in EVP_KDF_CTX<\/small><\/b> (3).<\/p>\n EVP_KDF_CTRL_SET_SCRYPT_N EVP_KDF_CTRL_SET_SCRYPT_N<\/small><\/b> expects one argument: “uint64_t N”<\/p>\n EVP_KDF_CTRL_SET_SCRYPT_R<\/small><\/b> expects one argument: “uint32_t r”<\/p>\n EVP_KDF_CTRL_SET_SCRYPT_P<\/small><\/b> expects one argument: “uint32_t p”<\/p>\n These controls configure the scrypt work factors N, r and p.<\/p>\n EVP_KDF_ctrl_str()<\/b> type strings: “N”, “r” and “p”, respectively.<\/p>\n The corresponding value strings are expected to be decimal numbers.<\/p>\n A context for scrypt can be obtained by calling:<\/p>\n EVP_KDF_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_SCRYPT);<\/p>\n The output length of an scrypt key derivation is specified via the keylen<\/b> parameter to the EVP_KDF_derive<\/b>(3) function.<\/p>\n This example derives a 64\u2212byte long test vector using scrypt with the password “password”, salt “NaCl” and N = 1024, r = 8, p = 16.<\/p>\n EVP_KDF_CTX *kctx; RFC 7914<\/small><\/p>\n
DESCRIPTION<\/a>
NOTES<\/a>
EXAMPLE<\/a>
CONFORMING TO<\/a>
SEE ALSO<\/a>
COPYRIGHT<\/a> <\/p>\n
\nNAME <\/a> <\/h2>\n
DESCRIPTION <\/a> <\/h2>\n
EVP_KDF_SCRYPT<\/small><\/b> is the numeric identity for this implementation; it can be used with the EVP_KDF_CTX_new_id()<\/b> function.<\/p>\n
The supported controls are:
EVP_KDF_CTRL_SET_PASS
EVP_KDF_CTRL_SET_SALT<\/small><\/b><\/p>\n
EVP_KDF_CTRL_SET_SCRYPT_R
EVP_KDF_CTRL_SET_SCRYPT_P<\/small><\/b><\/p>\nNOTES <\/a> <\/h2>\n
EXAMPLE <\/a> <\/h2>\n
unsigned char out[64];
kctx = EVP_KDF_CTX_new_id(EVP_KDF_SCRYPT);
if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_PASS, “password”, (size_t)8) <= 0) {
error(“EVP_KDF_CTRL_SET_PASS”);
}
if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SALT, “NaCl”, (size_t)4) <= 0) {
error(“EVP_KDF_CTRL_SET_SALT”);
}
if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SCRYPT_N, (uint64_t)1024) <= 0) {
error(“EVP_KDF_CTRL_SET_SCRYPT_N”);
}
if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SCRYPT_R, (uint32_t)8) <= 0) {
error(“EVP_KDF_CTRL_SET_SCRYPT_R”);
}
if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SCRYPT_P, (uint32_t)16) <= 0) {
error(“EVP_KDF_CTRL_SET_SCRYPT_P”);
}
if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) {
error(“EVP_KDF_derive”);
}
{
const unsigned char expected[sizeof(out)] = {
0xfd, 0xba, 0xbe, 0x1c, 0x9d, 0x34, 0x72, 0x00,
0x78, 0x56, 0xe7, 0x19, 0x0d, 0x01, 0xe9, 0xfe,
0x7c, 0x6a, 0xd7, 0xcb, 0xc8, 0x23, 0x78, 0x30,
0xe7, 0x73, 0x76, 0x63, 0x4b, 0x37, 0x31, 0x62,
0x2e, 0xaf, 0x30, 0xd9, 0x2e, 0x22, 0xa3, 0x88,
0x6f, 0xf1, 0x09, 0x27, 0x9d, 0x98, 0x30, 0xda,
0xc7, 0x27, 0xaf, 0xb9, 0x4a, 0x83, 0xee, 0x6d,
0x83, 0x60, 0xcb, 0xdf, 0xa2, 0xcc, 0x06, 0x40
};
assert(!memcmp(out, expected, sizeof(out)));
}
EVP_KDF_CTX_free(kctx);<\/p>\nCONFORMING TO <\/a> <\/h2>\n
SEE ALSO <\/a> <\/h2>\n