178 lines
5.8 KiB
HTML
178 lines
5.8 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SCRYPT</TITLE>
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</HEAD><BODY>
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<H1>SCRYPT</H1>
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Section: OpenSSL (7SSL)<BR>Updated: 2021-03-22<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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scrypt - EVP_PKEY scrypt KDF support
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<A NAME="lbAC"> </A>
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<H2>DESCRIPTION</H2>
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The <FONT SIZE="-1">EVP_PKEY_SCRYPT</FONT> algorithm implements the scrypt password based key
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derivation function, as described in <FONT SIZE="-1">RFC 7914.</FONT> It is memory-hard in the sense
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that it deliberately requires a significant amount of <FONT SIZE="-1">RAM</FONT> 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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<P>
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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 <FONT SIZE="-1">CPU</FONT>
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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 <FONT SIZE="-1">RAM</FONT> that scrypt requires for its computation
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is roughly (128 * N * r * p) bytes.
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<P>
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In the original paper of Colin Percival (``Stronger Key Derivation via
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Sequential Memory-Hard Functions'', 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 <FONT SIZE="-1">CPU</FONT> (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 default amount of <FONT SIZE="-1">RAM</FONT> that
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may be used by scrypt defaults to 1025 MiB.
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<A NAME="lbAD"> </A>
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<H2>NOTES</H2>
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A context for scrypt can be obtained by calling:
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<P>
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<PRE>
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EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SCRYPT, NULL);
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</PRE>
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<P>
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The output length of an scrypt key derivation is specified via the
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length parameter to the <B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_derive">EVP_PKEY_derive</A></B>(3) function.
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<A NAME="lbAE"> </A>
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<H2>EXAMPLES</H2>
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This example derives a 64-byte long test vector using scrypt using the password
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``password'', salt ``NaCl'' and N = 1024, r = 8, p = 16.
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<P>
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<PRE>
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EVP_PKEY_CTX *pctx;
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unsigned char out[64];
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size_t outlen = sizeof(out);
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pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SCRYPT, NULL);
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if (EVP_PKEY_derive_init(pctx) <= 0) {
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error("EVP_PKEY_derive_init");
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}
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if (EVP_PKEY_CTX_set1_pbe_pass(pctx, "password", 8) <= 0) {
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error("EVP_PKEY_CTX_set1_pbe_pass");
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}
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if (EVP_PKEY_CTX_set1_scrypt_salt(pctx, "NaCl", 4) <= 0) {
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error("EVP_PKEY_CTX_set1_scrypt_salt");
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}
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if (EVP_PKEY_CTX_set_scrypt_N(pctx, 1024) <= 0) {
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error("EVP_PKEY_CTX_set_scrypt_N");
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}
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if (EVP_PKEY_CTX_set_scrypt_r(pctx, 8) <= 0) {
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error("EVP_PKEY_CTX_set_scrypt_r");
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}
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if (EVP_PKEY_CTX_set_scrypt_p(pctx, 16) <= 0) {
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error("EVP_PKEY_CTX_set_scrypt_p");
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}
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if (EVP_PKEY_derive(pctx, out, &outlen) <= 0) {
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error("EVP_PKEY_derive");
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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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assert(!memcmp(out, expected, sizeof(out)));
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}
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EVP_PKEY_CTX_free(pctx);
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</PRE>
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<A NAME="lbAF"> </A>
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<H2>CONFORMING TO</H2>
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<FONT SIZE="-1">RFC 7914</FONT>
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<A NAME="lbAG"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_CTX_set1_scrypt_salt">EVP_PKEY_CTX_set1_scrypt_salt</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_CTX_set_scrypt_N">EVP_PKEY_CTX_set_scrypt_N</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_CTX_set_scrypt_r">EVP_PKEY_CTX_set_scrypt_r</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_CTX_set_scrypt_p">EVP_PKEY_CTX_set_scrypt_p</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_CTX_set_scrypt_maxmem_bytes">EVP_PKEY_CTX_set_scrypt_maxmem_bytes</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_CTX_new">EVP_PKEY_CTX_new</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_CTX_ctrl_str">EVP_PKEY_CTX_ctrl_str</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+EVP_PKEY_derive">EVP_PKEY_derive</A></B>(3)
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<A NAME="lbAH"> </A>
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<H2>COPYRIGHT</H2>
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Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.
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<P>
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Licensed under the OpenSSL license (the ``License''). 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 <FONT SIZE="-1">LICENSE</FONT> in the source distribution or at
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<<A HREF="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</A>>.
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">DESCRIPTION</A><DD>
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<DT id="3"><A HREF="#lbAD">NOTES</A><DD>
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<DT id="4"><A HREF="#lbAE">EXAMPLES</A><DD>
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<DT id="5"><A HREF="#lbAF">CONFORMING TO</A><DD>
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<DT id="6"><A HREF="#lbAG">SEE ALSO</A><DD>
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<DT id="7"><A HREF="#lbAH">COPYRIGHT</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:06:09 GMT, March 31, 2021
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</BODY>
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</HTML>
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