280 lines
13 KiB
HTML
280 lines
13 KiB
HTML
<!DOCTYPE html>
|
|
<html>
|
|
<head>
|
|
<meta charset="utf-8"/>
|
|
<style>
|
|
table.head, table.foot { width: 100%; }
|
|
td.head-rtitle, td.foot-os { text-align: right; }
|
|
td.head-vol { text-align: center; }
|
|
div.Pp { margin: 1ex 0ex; }
|
|
</style>
|
|
<link rel="stylesheet" href="style.css" type="text/css" media="all"/>
|
|
<title>CRYPTO_BLAKE2B(3MONOCYPHER)</title>
|
|
</head>
|
|
<body>
|
|
<table class="head">
|
|
<tr>
|
|
<td class="head-ltitle">CRYPTO_BLAKE2B(3MONOCYPHER)</td>
|
|
<td class="head-vol">3MONOCYPHER</td>
|
|
<td class="head-rtitle">CRYPTO_BLAKE2B(3MONOCYPHER)</td>
|
|
</tr>
|
|
</table>
|
|
<div class="manual-text">
|
|
<h1 class="Sh" title="Sh" id="NAME"><a class="selflink" href="#NAME">NAME</a></h1>
|
|
<b class="Nm" title="Nm">crypto_blake2b</b>,
|
|
<b class="Nm" title="Nm">crypto_blake2b_general</b>,
|
|
<b class="Nm" title="Nm">crypto_blake2b_general_init</b>,
|
|
<b class="Nm" title="Nm">crypto_blake2b_init</b>,
|
|
<b class="Nm" title="Nm">crypto_blake2b_update</b>,
|
|
<b class="Nm" title="Nm">crypto_blake2b_final</b> —
|
|
<span class="Nd" title="Nd">cryptographic hashing</span>
|
|
<h1 class="Sh" title="Sh" id="SYNOPSIS"><a class="selflink" href="#SYNOPSIS">SYNOPSIS</a></h1>
|
|
<b class="In" title="In">#include
|
|
<<a class="In" title="In">monocypher.h</a>></b>
|
|
<div class="Pp"></div>
|
|
<var class="Ft" title="Ft">void</var>
|
|
<br/>
|
|
<b class="Fn" title="Fn">crypto_blake2b</b>(<var class="Fa" title="Fa">uint8_t
|
|
hash[64]</var>, <var class="Fa" title="Fa">const uint8_t *message</var>,
|
|
<var class="Fa" title="Fa">size_t message_size</var>);
|
|
<div class="Pp"></div>
|
|
<var class="Ft" title="Ft">void</var>
|
|
<br/>
|
|
<b class="Fn" title="Fn">crypto_blake2b_general</b>(<var class="Fa" title="Fa">uint8_t
|
|
*hash</var>, <var class="Fa" title="Fa">size_t hash_size</var>,
|
|
<var class="Fa" title="Fa">const uint8_t *key</var>,
|
|
<var class="Fa" title="Fa">size_t key_size</var>,
|
|
<var class="Fa" title="Fa">const uint8_t *message</var>,
|
|
<var class="Fa" title="Fa">size_t message_size</var>);
|
|
<div class="Pp"></div>
|
|
<var class="Ft" title="Ft">void</var>
|
|
<br/>
|
|
<b class="Fn" title="Fn">crypto_blake2b_init</b>(<var class="Fa" title="Fa">crypto_blake2b_ctx
|
|
*ctx</var>);
|
|
<div class="Pp"></div>
|
|
<var class="Ft" title="Ft">void</var>
|
|
<br/>
|
|
<b class="Fn" title="Fn">crypto_blake2b_general_init</b>(<var class="Fa" title="Fa">crypto_blake2b_ctx
|
|
*ctx</var>, <var class="Fa" title="Fa">size_t hash_size</var>,
|
|
<var class="Fa" title="Fa">const uint8_t *key</var>,
|
|
<var class="Fa" title="Fa">size_t key_size</var>);
|
|
<div class="Pp"></div>
|
|
<var class="Ft" title="Ft">void</var>
|
|
<br/>
|
|
<b class="Fn" title="Fn">crypto_blake2b_update</b>(<var class="Fa" title="Fa">crypto_blake2b_ctx
|
|
*ctx</var>, <var class="Fa" title="Fa">const uint8_t *message</var>,
|
|
<var class="Fa" title="Fa">size_t message_size</var>);
|
|
<div class="Pp"></div>
|
|
<var class="Ft" title="Ft">void</var>
|
|
<br/>
|
|
<b class="Fn" title="Fn">crypto_blake2b_final</b>(<var class="Fa" title="Fa">crypto_blake2b_ctx
|
|
*ctx</var>, <var class="Fa" title="Fa">uint8_t *hash</var>);
|
|
<h1 class="Sh" title="Sh" id="DESCRIPTION"><a class="selflink" href="#DESCRIPTION">DESCRIPTION</a></h1>
|
|
BLAKE2b is a fast cryptographically secure hash, based on the ideas of Chacha20.
|
|
It is faster than MD5, yet just as secure as SHA-3.
|
|
<div class="Pp"></div>
|
|
Note that BLAKE2b itself is not suitable for hashing passwords and deriving keys
|
|
from them; use the
|
|
<a class="Xr" title="Xr" href="crypto_argon2i.html">crypto_argon2i(3monocypher)</a>
|
|
family of functions for that purpose instead.
|
|
<div class="Pp"></div>
|
|
BLAKE2b is immune to length extension attacks, and as such does not require any
|
|
specific precautions, such as using the HMAC algorithm.
|
|
<div class="Pp"></div>
|
|
The arguments are:
|
|
<dl class="Bl-tag">
|
|
<dt class="It-tag"> </dt>
|
|
<dd class="It-tag"> </dd>
|
|
<dt class="It-tag"><var class="Fa" title="Fa">hash</var></dt>
|
|
<dd class="It-tag">The output hash.</dd>
|
|
<dt class="It-tag"> </dt>
|
|
<dd class="It-tag"> </dd>
|
|
<dt class="It-tag"><var class="Fa" title="Fa">hash_size</var></dt>
|
|
<dd class="It-tag">Length of <var class="Fa" title="Fa">hash</var>, in bytes.
|
|
Must be between 1 and 64. Anything below 32 is discouraged when using
|
|
Blake2b as a general-purpose hash function; anything below 16 is
|
|
discouraged when using Blake2b as a message authentication code.</dd>
|
|
<dt class="It-tag"> </dt>
|
|
<dd class="It-tag"> </dd>
|
|
<dt class="It-tag"><var class="Fa" title="Fa">key</var></dt>
|
|
<dd class="It-tag">Some secret key. One cannot predict the final hash without
|
|
it. May be <code class="Dv" title="Dv">NULL</code> if
|
|
<var class="Fa" title="Fa">key_size</var> is 0, in which case no key is
|
|
used. Keys can be used to create a message authentication code (MAC). Use
|
|
<a class="Xr" title="Xr" href="crypto_verify16.html">crypto_verify16(3monocypher)</a>,
|
|
<a class="Xr" title="Xr" href="crypto_verify32.html">crypto_verify32(3monocypher)</a>,
|
|
or
|
|
<a class="Xr" title="Xr" href="crypto_verify64.html">crypto_verify64(3monocypher)</a>
|
|
to compare MACs created this way. Choose the size of the hash accordingly.
|
|
Users may want to wipe the key with
|
|
<a class="Xr" title="Xr" href="crypto_wipe.html">crypto_wipe(3monocypher)</a>
|
|
once they are done with it.</dd>
|
|
<dt class="It-tag"> </dt>
|
|
<dd class="It-tag"> </dd>
|
|
<dt class="It-tag"><var class="Fa" title="Fa">key_size</var></dt>
|
|
<dd class="It-tag">Length of <var class="Fa" title="Fa">key</var>, in bytes.
|
|
Must be between 0 and 64. 32 is a good default.</dd>
|
|
<dt class="It-tag"> </dt>
|
|
<dd class="It-tag"> </dd>
|
|
<dt class="It-tag"><var class="Fa" title="Fa">message</var></dt>
|
|
<dd class="It-tag">The message to hash. May overlap with
|
|
<var class="Fa" title="Fa">hash</var>. May be
|
|
<code class="Dv" title="Dv">NULL</code> if
|
|
<var class="Fa" title="Fa">message_size</var> is 0.</dd>
|
|
<dt class="It-tag"> </dt>
|
|
<dd class="It-tag"> </dd>
|
|
<dt class="It-tag"><var class="Fa" title="Fa">message_size</var></dt>
|
|
<dd class="It-tag">Length of <var class="Fa" title="Fa">message</var>, in
|
|
bytes.</dd>
|
|
</dl>
|
|
<h2 class="Ss" title="Ss" id="Direct_interface"><a class="selflink" href="#Direct_interface">Direct
|
|
interface</a></h2>
|
|
The direct interface has two functions,
|
|
<b class="Fn" title="Fn">crypto_blake2b</b>() and
|
|
<b class="Fn" title="Fn">crypto_blake2b_general</b>().
|
|
<b class="Fn" title="Fn">crypto_blake2b</b>() is provided for convenience, and
|
|
is equivalent to calling <b class="Fn" title="Fn">crypto_blake2b_general</b>()
|
|
with no key and a 64-byte hash.
|
|
<div class="Pp"></div>
|
|
<b class="Fn" title="Fn">crypto_blake2b_general</b>() users can specify the size
|
|
of the hash, and use a secret key to make the hash unpredictable –
|
|
useful for message authentication codes. Even when using a key, you do not
|
|
have to wipe the context struct with
|
|
<a class="Xr" title="Xr" href="crypto_wipe.html">crypto_wipe(3monocypher)</a>.
|
|
<h2 class="Ss" title="Ss" id="Incremental_interface"><a class="selflink" href="#Incremental_interface">Incremental
|
|
interface</a></h2>
|
|
The incremental interface is useful for handling streams of data or large files
|
|
without using too much memory. This interface uses three steps:
|
|
<ul class="Bl-bullet">
|
|
<li class="It-bullet">initialisation with
|
|
<b class="Fn" title="Fn">crypto_blake2b_general_init</b>() or
|
|
<b class="Fn" title="Fn">crypto_blake2b_init</b>(), which sets up a
|
|
context with the hashing parameters;</li>
|
|
<li class="It-bullet">update with
|
|
<b class="Fn" title="Fn">crypto_blake2b_update</b>(), which hashes the
|
|
message chunk by chunk, and keep the intermediary result in the
|
|
context;</li>
|
|
<li class="It-bullet">and finalisation with
|
|
<b class="Fn" title="Fn">crypto_blake2b_final</b>(), which produces the
|
|
final hash. The <var class="Ft" title="Ft">crypto_blake2b_ctx</var> is
|
|
automatically wiped upon finalisation.</li>
|
|
</ul>
|
|
<div class="Pp"></div>
|
|
The invariants of the parameters are the same as for
|
|
<b class="Fn" title="Fn">crypto_blake2b_general</b>().
|
|
<b class="Fn" title="Fn">crypto_blake2b_init</b>() is a convenience
|
|
initialisation function that specifies a 64-byte hash and no key. This is
|
|
considered a good default.
|
|
<h1 class="Sh" title="Sh" id="RETURN_VALUES"><a class="selflink" href="#RETURN_VALUES">RETURN
|
|
VALUES</a></h1>
|
|
These functions return nothing.
|
|
<h1 class="Sh" title="Sh" id="EXAMPLES"><a class="selflink" href="#EXAMPLES">EXAMPLES</a></h1>
|
|
The following examples assume the existence of
|
|
<b class="Fn" title="Fn">arc4random_buf</b>(), which fills the given buffer
|
|
with cryptographically secure random bytes. If
|
|
<b class="Fn" title="Fn">arc4random_buf</b>() does not exist on your system,
|
|
see <a class="Xr" title="Xr" href="intro.html">intro(3monocypher)</a> for
|
|
advice about how to generate cryptographically secure random bytes.
|
|
<div class="Pp"></div>
|
|
Hashing a message all at once:
|
|
<div class="Pp"></div>
|
|
<div class="Bd" style="margin-left: 5.00ex;">
|
|
<pre class="Li">
|
|
uint8_t hash [64]; /* Output hash (64 bytes) */
|
|
uint8_t message[12] = "Lorem ipsum"; /* Message to hash */
|
|
crypto_blake2b(hash, message, 12);
|
|
</pre>
|
|
</div>
|
|
<div class="Pp"></div>
|
|
Computing a message authentication code all at once:
|
|
<div class="Pp"></div>
|
|
<div class="Bd" style="margin-left: 5.00ex;">
|
|
<pre class="Li">
|
|
uint8_t hash [16];
|
|
uint8_t key [32];
|
|
uint8_t message[11] = "Lorem ipsu"; /* Message to authenticate */
|
|
arc4random_buf(key, 32);
|
|
crypto_blake2b_general(hash, 16, key, 32, message, 11);
|
|
/* Wipe secrets if they are no longer needed */
|
|
crypto_wipe(message, 11);
|
|
crypto_wipe(key, 32);
|
|
</pre>
|
|
</div>
|
|
<div class="Pp"></div>
|
|
Hashing a message incrementally (without a key):
|
|
<div class="Pp"></div>
|
|
<div class="Bd" style="margin-left: 5.00ex;">
|
|
<pre class="Li">
|
|
uint8_t hash [ 64]; /* Output hash (64 bytes) */
|
|
uint8_t message[500] = {1}; /* Message to hash */
|
|
crypto_blake2b_ctx ctx;
|
|
crypto_blake2b_init(&ctx);
|
|
for (size_t i = 0; i < 500; i += 100) {
|
|
crypto_blake2b_update(&ctx, message + i, 100);
|
|
}
|
|
crypto_blake2b_final(&ctx, hash);
|
|
</pre>
|
|
</div>
|
|
<div class="Pp"></div>
|
|
Computing a message authentication code incrementally:
|
|
<div class="Pp"></div>
|
|
<div class="Bd" style="margin-left: 5.00ex;">
|
|
<pre class="Li">
|
|
uint8_t hash [ 16];
|
|
uint8_t key [ 32];
|
|
uint8_t message[500] = {1}; /* Message to authenticate */
|
|
crypto_blake2b_ctx ctx;
|
|
arc4random_buf(key, 32);
|
|
crypto_blake2b_general_init(&ctx, 16, key, 32);
|
|
/* Wipe the key */
|
|
crypto_wipe(key, 32);
|
|
for (size_t i = 0; i < 500; i += 100) {
|
|
crypto_blake2b_update(&ctx, message + i, 100);
|
|
/* Wipe secrets if they are no longer needed */
|
|
crypto_wipe(message + i, 100);
|
|
}
|
|
crypto_blake2b_final(&ctx, hash);
|
|
</pre>
|
|
</div>
|
|
<h1 class="Sh" title="Sh" id="SEE_ALSO"><a class="selflink" href="#SEE_ALSO">SEE
|
|
ALSO</a></h1>
|
|
<a class="Xr" title="Xr" href="crypto_key_exchange.html">crypto_key_exchange(3monocypher)</a>,
|
|
<a class="Xr" title="Xr" href="crypto_lock.html">crypto_lock(3monocypher)</a>,
|
|
<a class="Xr" title="Xr" href="intro.html">intro(3monocypher)</a>
|
|
<h1 class="Sh" title="Sh" id="STANDARDS"><a class="selflink" href="#STANDARDS">STANDARDS</a></h1>
|
|
These functions implement BLAKE2b, described in RFC 7693.
|
|
<h1 class="Sh" title="Sh" id="HISTORY"><a class="selflink" href="#HISTORY">HISTORY</a></h1>
|
|
The <b class="Fn" title="Fn">crypto_blake2b</b>(),
|
|
<b class="Fn" title="Fn">crypto_blake2b_general</b>(),
|
|
<b class="Fn" title="Fn">crypto_blake2b_general_init</b>(),
|
|
<b class="Fn" title="Fn">crypto_blake2b_init</b>(),
|
|
<b class="Fn" title="Fn">crypto_blake2b_update</b>(), and
|
|
<b class="Fn" title="Fn">crypto_blake2b_final</b>() functions first appeared
|
|
in Monocypher 0.1.
|
|
<h1 class="Sh" title="Sh" id="CAVEATS"><a class="selflink" href="#CAVEATS">CAVEATS</a></h1>
|
|
Monocypher does not perform any input validation. Any deviation from the
|
|
specified input and output length ranges results in
|
|
<b class="Sy" title="Sy">undefined behaviour</b>. Make sure your inputs are
|
|
correct.
|
|
<h1 class="Sh" title="Sh" id="SECURITY_CONSIDERATIONS"><a class="selflink" href="#SECURITY_CONSIDERATIONS">SECURITY
|
|
CONSIDERATIONS</a></h1>
|
|
BLAKE2b is a general-purpose cryptographic hash function; this means that it is
|
|
not suited for hashing passwords and deriving cryptographic keys from
|
|
passwords in particular. While cryptographic keys usually have hundreds of
|
|
bits of entropy, passwords are often much less complex. When storing passwords
|
|
as hashes or when deriving keys from them, the goal is normally to prevent
|
|
attackers from quickly iterating all possible passwords. Because passwords
|
|
tend to be simple, it is important to artificially slow down attackers by
|
|
using especially computationally difficult hashing algorithms. Monocypher
|
|
therefore provides
|
|
<a class="Xr" title="Xr" href="crypto_argon2i.html">crypto_argon2i(3monocypher)</a>
|
|
for password hashing and deriving keys from passwords.</div>
|
|
<table class="foot">
|
|
<tr>
|
|
<td class="foot-date">March 31, 2020</td>
|
|
<td class="foot-os">Linux 4.15.0-106-generic</td>
|
|
</tr>
|
|
</table>
|
|
</body>
|
|
</html>
|