268 lines
9.6 KiB
Groff
Executable File
268 lines
9.6 KiB
Groff
Executable File
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.\" ========================================================================
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.\"
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.IX Title "EVP_KDF-SCRYPT 7"
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.TH EVP_KDF-SCRYPT 7 "2020-03-02" "3.0.0-dev" "OpenSSL"
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH "NAME"
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EVP_KDF\-SCRYPT \- The scrypt EVP_KDF implementation
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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Support for computing the \fBscrypt\fR password-based \s-1KDF\s0 through the \fB\s-1EVP_KDF\s0\fR
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\&\s-1API\s0.
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.PP
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The \s-1EVP_KDF\-SCRYPT\s0 algorithm implements the scrypt password-based key
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derivation function, as described in \s-1RFC\s0 7914. It is memory-hard in the sense
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that it deliberately requires a significant amount of \s-1RAM\s0 for efficient
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computation. The intention of this is to render brute forcing of passwords on
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systems that lack large amounts of main memory (such as GPUs or ASICs)
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computationally infeasible.
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.PP
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scrypt provides three work factors that can be customized: N, r and p. N, which
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has to be a positive power of two, is the general work factor and scales \s-1CPU\s0
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time in an approximately linear fashion. r is the block size of the internally
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used hash function and p is the parallelization factor. Both r and p need to be
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greater than zero. The amount of \s-1RAM\s0 that scrypt requires for its computation
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is roughly (128 * N * r * p) bytes.
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.PP
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In the original paper of Colin Percival (\*(L"Stronger Key Derivation via
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Sequential Memory-Hard Functions\*(R", 2009), the suggested values that give a
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computation time of less than 5 seconds on a 2.5 GHz Intel Core 2 Duo are N =
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2^20 = 1048576, r = 8, p = 1. Consequently, the required amount of memory for
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this computation is roughly 1 GiB. On a more recent \s-1CPU\s0 (Intel i7\-5930K at 3.5
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GHz), this computation takes about 3 seconds. When N, r or p are not specified,
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they default to 1048576, 8, and 1, respectively. The maximum amount of \s-1RAM\s0 that
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may be used by scrypt defaults to 1025 MiB.
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.SS "Identity"
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.IX Subsection "Identity"
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\&\*(L"\s-1SCRYPT\s0\*(R" is the name for this implementation; it
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can be used with the \fIEVP_KDF_fetch()\fR function.
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.SS "Supported parameters"
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.IX Subsection "Supported parameters"
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The supported parameters are:
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.ie n .IP """pass"" (\fB\s-1OSSL_KDF_PARAM_PASSWORD\s0\fR) <octet string>" 4
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.el .IP "``pass'' (\fB\s-1OSSL_KDF_PARAM_PASSWORD\s0\fR) <octet string>" 4
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.IX Item "pass (OSSL_KDF_PARAM_PASSWORD) <octet string>"
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.PD 0
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.ie n .IP """salt"" (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) <octet string>" 4
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.el .IP "``salt'' (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) <octet string>" 4
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.IX Item "salt (OSSL_KDF_PARAM_SALT) <octet string>"
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.PD
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These parameters work as described in \*(L"\s-1PARAMETERS\s0\*(R" in \s-1\fIEVP_KDF\s0\fR\|(3).
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.ie n .IP """n"" (\fB\s-1OSSL_KDF_PARAM_SCRYPT_N\s0\fR) <unsigned integer>" 4
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.el .IP "``n'' (\fB\s-1OSSL_KDF_PARAM_SCRYPT_N\s0\fR) <unsigned integer>" 4
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.IX Item "n (OSSL_KDF_PARAM_SCRYPT_N) <unsigned integer>"
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.PD 0
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.ie n .IP """r"" (\fB\s-1OSSL_KDF_PARAM_SCRYPT_R\s0\fR) <unsigned integer>" 4
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.el .IP "``r'' (\fB\s-1OSSL_KDF_PARAM_SCRYPT_R\s0\fR) <unsigned integer>" 4
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.IX Item "r (OSSL_KDF_PARAM_SCRYPT_R) <unsigned integer>"
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.ie n .IP """p"" (\fB\s-1OSSL_KDF_PARAM_SCRYPT_P\s0\fR) <unsigned integer>" 4
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.el .IP "``p'' (\fB\s-1OSSL_KDF_PARAM_SCRYPT_P\s0\fR) <unsigned integer>" 4
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.IX Item "p (OSSL_KDF_PARAM_SCRYPT_P) <unsigned integer>"
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.PD
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These parameters configure the scrypt work factors N, r and p.
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N is a parameter of type \fBuint64_t\fR.
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Both r and p are parameters of type \fBuint32_t\fR.
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.SH "NOTES"
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.IX Header "NOTES"
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A context for scrypt can be obtained by calling:
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.PP
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.Vb 2
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\& EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SCRYPT", NULL);
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\& EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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.Ve
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.PP
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The output length of an scrypt key derivation is specified via the
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\&\*(L"keylen\*(R" parameter to the \fIEVP_KDF_derive\fR\|(3) function.
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.SH "EXAMPLES"
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.IX Header "EXAMPLES"
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This example derives a 64\-byte long test vector using scrypt with the password
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\&\*(L"password\*(R", salt \*(L"NaCl\*(R" and N = 1024, r = 8, p = 16.
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.PP
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.Vb 4
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\& EVP_KDF *kdf;
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\& EVP_KDF_CTX *kctx;
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\& unsigned char out[64];
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\& OSSL_PARAM params[6], *p = params;
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\&
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\& kdf = EVP_KDF_fetch(NULL, "SCRYPT", NULL);
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\& kctx = EVP_KDF_CTX_new(kdf);
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\& EVP_KDF_free(kdf);
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\&
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\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_PASSWORD,
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\& "password", (size_t)8);
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\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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\& "NaCl", (size_t)4);
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\& *p++ = OSSL_PARAM_construct_uint64(OSSL_KDF_PARAM_SCRYPT_N, (uint64_t)1024);
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\& *p++ = OSSL_PARAM_construct_uint32(OSSL_KDF_PARAM_SCRYPT_R, (uint32_t)8);
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\& *p++ = OSSL_PARAM_construct_uint32(OSSL_KDF_PARAM_SCRYPT_P, (uint32_t)16);
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\& *p = OSSL_PARAM_construct_end();
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\& if (EVP_KDF_CTX_set_params(kctx, params) <= 0) {
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\& error("EVP_KDF_CTX_set_params");
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\& }
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\& if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) {
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\& error("EVP_KDF_derive");
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\& }
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\&
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\& {
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\& const unsigned char expected[sizeof(out)] = {
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\& 0xfd, 0xba, 0xbe, 0x1c, 0x9d, 0x34, 0x72, 0x00,
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\& 0x78, 0x56, 0xe7, 0x19, 0x0d, 0x01, 0xe9, 0xfe,
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\& 0x7c, 0x6a, 0xd7, 0xcb, 0xc8, 0x23, 0x78, 0x30,
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\& 0xe7, 0x73, 0x76, 0x63, 0x4b, 0x37, 0x31, 0x62,
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\& 0x2e, 0xaf, 0x30, 0xd9, 0x2e, 0x22, 0xa3, 0x88,
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\& 0x6f, 0xf1, 0x09, 0x27, 0x9d, 0x98, 0x30, 0xda,
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\& 0xc7, 0x27, 0xaf, 0xb9, 0x4a, 0x83, 0xee, 0x6d,
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\& 0x83, 0x60, 0xcb, 0xdf, 0xa2, 0xcc, 0x06, 0x40
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\& };
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\&
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\& assert(!memcmp(out, expected, sizeof(out)));
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\& }
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\&
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\& EVP_KDF_CTX_free(kctx);
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.Ve
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.SH "CONFORMING TO"
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.IX Header "CONFORMING TO"
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\&\s-1RFC\s0 7914
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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\&\s-1\fIEVP_KDF\s0\fR\|(3),
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\&\fIEVP_KDF_CTX_new\fR\|(3),
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\&\fIEVP_KDF_CTX_free\fR\|(3),
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\&\fIEVP_KDF_CTX_set_params\fR\|(3),
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\&\fIEVP_KDF_derive\fR\|(3),
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\&\*(L"\s-1PARAMETERS\s0\*(R" in \s-1\fIEVP_KDF\s0\fR\|(3)
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.SH "COPYRIGHT"
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.IX Header "COPYRIGHT"
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Copyright 2017\-2019 The OpenSSL Project Authors. All Rights Reserved.
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.PP
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Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file \s-1LICENSE\s0 in the source distribution or at
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<https://www.openssl.org/source/license.html>.
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