180 lines
8.3 KiB
HTML
180 lines
8.3 KiB
HTML
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8"/>
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<style>
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table.head, table.foot { width: 100%; }
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td.head-rtitle, td.foot-os { text-align: right; }
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td.head-vol { text-align: center; }
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div.Pp { margin: 1ex 0ex; }
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</style>
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<link rel="stylesheet" href="style.css" type="text/css" media="all"/>
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<title>CRYPTO_SHA512(3MONOCYPHER)</title>
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</head>
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<body>
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<table class="head">
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<tr>
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<td class="head-ltitle">CRYPTO_SHA512(3MONOCYPHER)</td>
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<td class="head-vol">3MONOCYPHER</td>
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<td class="head-rtitle">CRYPTO_SHA512(3MONOCYPHER)</td>
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</tr>
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</table>
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<div class="manual-text">
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<h1 class="Sh" title="Sh" id="NAME"><a class="selflink" href="#NAME">NAME</a></h1>
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<b class="Nm" title="Nm">crypto_sha512</b>,
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<b class="Nm" title="Nm">crypto_sha512_init</b>,
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<b class="Nm" title="Nm">crypto_sha512_update</b>,
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<b class="Nm" title="Nm">crypto_sha512_final</b> —
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<span class="Nd" title="Nd">cryptographic hashing with the SHA-512
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algorithm</span>
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<h1 class="Sh" title="Sh" id="SYNOPSIS"><a class="selflink" href="#SYNOPSIS">SYNOPSIS</a></h1>
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<b class="In" title="In">#include
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<<a class="In" title="In">monocypher-ed25519.h</a>></b>
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<div class="Pp"></div>
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<var class="Ft" title="Ft">void</var>
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<br/>
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<b class="Fn" title="Fn">crypto_sha512</b>(<var class="Fa" title="Fa">uint8_t
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hash[64]</var>, <var class="Fa" title="Fa">const uint8_t *message</var>,
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<var class="Fa" title="Fa">size_t message_size</var>);
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<div class="Pp"></div>
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<var class="Ft" title="Ft">void</var>
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<br/>
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<b class="Fn" title="Fn">crypto_sha512_init</b>(<var class="Fa" title="Fa">crypto_sha512_ctx
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*ctx</var>);
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<div class="Pp"></div>
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<var class="Ft" title="Ft">void</var>
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<br/>
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<b class="Fn" title="Fn">crypto_sha512_update</b>(<var class="Fa" title="Fa">crypto_sha512_ctx
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*ctx</var>, <var class="Fa" title="Fa">const uint8_t *message</var>,
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<var class="Fa" title="Fa">size_t message_size</var>);
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<div class="Pp"></div>
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<var class="Ft" title="Ft">void</var>
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<br/>
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<b class="Fn" title="Fn">crypto_sha512_final</b>(<var class="Fa" title="Fa">crypto_sha512_ctx
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*ctx</var>, <var class="Fa" title="Fa">uint8_t hash[64]</var>);
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<h1 class="Sh" title="Sh" id="DESCRIPTION"><a class="selflink" href="#DESCRIPTION">DESCRIPTION</a></h1>
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SHA-512 is a cryptographically secure hash, provided to enable compatibility
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with other cryptographic systems. It is generally recommended to use
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<a class="Xr" title="Xr" href="crypto_blake2b.html">crypto_blake2b(3monocypher)</a>
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instead, as it both performs faster on x86_64 CPUs and lacks many of the
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pitfalls of SHA-512.
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<div class="Pp"></div>
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Note that SHA-512 itself is not suitable for hashing passwords and deriving keys
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from them; use the
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<a class="Xr" title="Xr" href="crypto_argon2i.html">crypto_argon2i(3monocypher)</a>
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family of functions for that purpose instead.
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<div class="Pp"></div>
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SHA-512 is <i class="Em" title="Em">vulnerable to length extension attacks</i>;
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using it as a message authentication code (MAC) algorithm or keyed hash
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requires precautions. The
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<a class="Xr" title="Xr" href="crypto_hmac_sha512.html">crypto_hmac_sha512(3monocypher)</a>
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family of functions provides HMAC with SHA-512. Use
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<a class="Xr" title="Xr" href="crypto_verify64.html">crypto_verify64(3monocypher)</a>
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to compare MACs created this way.
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<div class="Pp"></div>
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The arguments are:
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<dl class="Bl-tag">
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<dt class="It-tag"> </dt>
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<dd class="It-tag"> </dd>
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<dt class="It-tag"><var class="Fa" title="Fa">hash</var></dt>
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<dd class="It-tag">The output hash, which is always 64 bytes long.</dd>
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<dt class="It-tag"> </dt>
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<dd class="It-tag"> </dd>
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<dt class="It-tag"><var class="Fa" title="Fa">message</var></dt>
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<dd class="It-tag">The message to hash. May overlap with
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<var class="Fa" title="Fa">hash</var>. May be
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<code class="Dv" title="Dv">NULL</code> if
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<var class="Fa" title="Fa">message_size</var> is 0.</dd>
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<dt class="It-tag"> </dt>
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<dd class="It-tag"> </dd>
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<dt class="It-tag"><var class="Fa" title="Fa">message_size</var></dt>
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<dd class="It-tag">Length of <var class="Fa" title="Fa">message</var>, in
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bytes.</dd>
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</dl>
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<div class="Pp"></div>
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An incremental interface is provided. It is useful for handling streams of data
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or large files without using too much memory. This interface uses three steps:
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<ul class="Bl-bullet">
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<li class="It-bullet">initialisation with
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<b class="Fn" title="Fn">crypto_sha512_init</b>(), which sets up a context
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with the hashing parameters;</li>
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<li class="It-bullet">update with
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<b class="Fn" title="Fn">crypto_sha512_update</b>(), which hashes the
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message chunk by chunk, and keep the intermediary result in the
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context;</li>
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<li class="It-bullet">and finalisation with
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<b class="Fn" title="Fn">crypto_sha512_final</b>(), which produces the
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final hash. The <var class="Ft" title="Ft">crypto_sha512_ctx</var> is
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automatically wiped upon finalisation.</li>
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</ul>
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<div class="Pp"></div>
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<b class="Fn" title="Fn">crypto_sha512</b>() is a convenience function that
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performs <b class="Fn" title="Fn">crypto_sha512_init</b>(),
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<b class="Fn" title="Fn">crypto_sha512_update</b>(), and
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<b class="Fn" title="Fn">crypto_sha512_final</b>().
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<h1 class="Sh" title="Sh" id="RETURN_VALUES"><a class="selflink" href="#RETURN_VALUES">RETURN
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VALUES</a></h1>
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These functions return nothing.
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<h1 class="Sh" title="Sh" id="EXAMPLES"><a class="selflink" href="#EXAMPLES">EXAMPLES</a></h1>
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Hashing a message all at once:
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<div class="Pp"></div>
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<div class="Bd" style="margin-left: 5.00ex;">
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<pre class="Li">
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uint8_t hash [64]; /* Output hash (64 bytes) */
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uint8_t message[12] = "Lorem ipsum"; /* Message to hash */
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crypto_sha512(hash, message, 12);
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</pre>
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</div>
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<div class="Pp"></div>
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Hashing a message incrementally:
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<div class="Pp"></div>
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<div class="Bd" style="margin-left: 5.00ex;">
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<pre class="Li">
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uint8_t hash [ 64]; /* Output hash (64 bytes) */
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uint8_t message[500] = {1}; /* Message to hash */
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crypto_sha512_ctx ctx;
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crypto_sha512_init(&ctx);
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for (size_t i = 0; i < 500; i += 100) {
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crypto_sha512_update(&ctx, message + i, 100);
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}
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crypto_sha512_final(&ctx, hash);
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</pre>
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</div>
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<h1 class="Sh" title="Sh" id="SEE_ALSO"><a class="selflink" href="#SEE_ALSO">SEE
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ALSO</a></h1>
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<a class="Xr" title="Xr" href="crypto_blake2b.html">crypto_blake2b(3monocypher)</a>,
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<a class="Xr" title="Xr" href="crypto_hmac_sha512.html">crypto_hmac_sha512(3monocypher)</a>,
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<a class="Xr" title="Xr" href="crypto_lock.html">crypto_lock(3monocypher)</a>,
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<a class="Xr" title="Xr" href="intro.html">intro(3monocypher)</a>
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<h1 class="Sh" title="Sh" id="STANDARDS"><a class="selflink" href="#STANDARDS">STANDARDS</a></h1>
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These functions implement SHA-512, described in RFC 6234 and the Federal
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Information Processing Standard (FIPS) 180-4.
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<h1 class="Sh" title="Sh" id="HISTORY"><a class="selflink" href="#HISTORY">HISTORY</a></h1>
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The <b class="Fn" title="Fn">crypto_sha512</b>(),
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<b class="Fn" title="Fn">crypto_sha512_init</b>(),
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<b class="Fn" title="Fn">crypto_sha512_update</b>(), and
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<b class="Fn" title="Fn">crypto_sha512_final</b>() functions first appeared in
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Monocypher 0.3; they were not intended for use outside Monocypher itself and
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thus undocumented. They became part of the official API in Monocypher 3.0.0.
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<h1 class="Sh" title="Sh" id="SECURITY_CONSIDERATIONS"><a class="selflink" href="#SECURITY_CONSIDERATIONS">SECURITY
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CONSIDERATIONS</a></h1>
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SHA-512 is a general-purpose cryptographic hash function; this means that it is
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not suited for hashing passwords and deriving cryptographic keys from
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passwords in particular. While cryptographic keys usually have hundreds of
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bits of entropy, passwords are often much less complex. When storing passwords
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as hashes or when deriving keys from them, the goal is normally to prevent
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attackers from quickly iterating all possible passwords. Because passwords
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tend to be simple, it is important to artificially slow down attackers by
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using especially computationally difficult hashing algorithms. Monocypher
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therefore provides
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<a class="Xr" title="Xr" href="crypto_argon2i.html">crypto_argon2i(3monocypher)</a>
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for password hashing and deriving keys from passwords.</div>
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<table class="foot">
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<tr>
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<td class="foot-date">February 5, 2020</td>
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<td class="foot-os">Linux 4.15.0-106-generic</td>
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</tr>
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</table>
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</body>
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</html>
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