Provided by: openssl_1.1.1c-1ubuntu4_amd64 bug

NAME

       scrypt - EVP_PKEY scrypt KDF support

DESCRIPTION

       The EVP_PKEY_SCRYPT algorithm implements the scrypt password based key derivation
       function, as described in RFC 7914.  It is memory-hard in the sense that it deliberately
       requires a significant amount of RAM 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.

       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 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 that scrypt requires for its computation is roughly (128 * N * r * p) bytes.

       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
       (Intel i7-5930K 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 default amount of RAM
       that may be used by scrypt defaults to 1025 MiB.

NOTES

       A context for scrypt can be obtained by calling:

        EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SCRYPT, NULL);

       The output length of an scrypt key derivation is specified via the length parameter to the
       EVP_PKEY_derive(3) function.

EXAMPLE

       This example derives a 64-byte long test vector using scrypt using the password
       "password", salt "NaCl" and N = 1024, r = 8, p = 16.

        EVP_PKEY_CTX *pctx;
        unsigned char out[64];

        size_t outlen = sizeof(out);
        pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SCRYPT, NULL);

        if (EVP_PKEY_derive_init(pctx) <= 0) {
            error("EVP_PKEY_derive_init");
        }
        if (EVP_PKEY_CTX_set1_pbe_pass(pctx, "password", 8) <= 0) {
            error("EVP_PKEY_CTX_set1_pbe_pass");
        }
        if (EVP_PKEY_CTX_set1_scrypt_salt(pctx, "NaCl", 4) <= 0) {
            error("EVP_PKEY_CTX_set1_scrypt_salt");
        }
        if (EVP_PKEY_CTX_set_scrypt_N(pctx, 1024) <= 0) {
            error("EVP_PKEY_CTX_set_scrypt_N");
        }
        if (EVP_PKEY_CTX_set_scrypt_r(pctx, 8) <= 0) {
            error("EVP_PKEY_CTX_set_scrypt_r");
        }
        if (EVP_PKEY_CTX_set_scrypt_p(pctx, 16) <= 0) {
            error("EVP_PKEY_CTX_set_scrypt_p");
        }
        if (EVP_PKEY_derive(pctx, out, &outlen) <= 0) {
            error("EVP_PKEY_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_PKEY_CTX_free(pctx);

CONFORMING TO

       RFC 7914

SEE ALSO

       EVP_PKEY_CTX_set1_scrypt_salt(3), EVP_PKEY_CTX_set_scrypt_N(3),
       EVP_PKEY_CTX_set_scrypt_r(3), EVP_PKEY_CTX_set_scrypt_p(3),
       EVP_PKEY_CTX_set_scrypt_maxmem_bytes(3), EVP_PKEY_CTX_new(3), EVP_PKEY_CTX_ctrl_str(3),
       EVP_PKEY_derive(3)

COPYRIGHT

       Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.