aboutsummaryrefslogtreecommitdiffstats
path: root/lib/crypto/doc
diff options
context:
space:
mode:
Diffstat (limited to 'lib/crypto/doc')
-rw-r--r--lib/crypto/doc/src/crypto.xml125
-rw-r--r--lib/crypto/doc/src/crypto_app.xml18
2 files changed, 141 insertions, 2 deletions
diff --git a/lib/crypto/doc/src/crypto.xml b/lib/crypto/doc/src/crypto.xml
index 464799b320..3a5efd0bea 100644
--- a/lib/crypto/doc/src/crypto.xml
+++ b/lib/crypto/doc/src/crypto.xml
@@ -790,9 +790,16 @@
<seealso marker="stdlib:rand">random number generation</seealso>,
in order to generate cryptographically strong random numbers
(based on OpenSSL's <c>BN_rand_range</c>),
- and saves it on process dictionary before returning it as well.
+ and saves it in the process dictionary before returning it as well.
See also
- <seealso marker="stdlib:rand#seed-1">rand:seed/1</seealso>.
+ <seealso marker="stdlib:rand#seed-1">rand:seed/1</seealso> and
+ <seealso marker="#rand_seed_s-0">rand_seed_s/0</seealso>.
+ </p>
+ <p>
+ When using the state object from this function the
+ <seealso marker="stdlib:rand">rand</seealso> functions using it
+ may throw exception <c>low_entropy</c> in case the random generator
+ failed due to lack of secure "randomness".
</p>
<p><em>Example</em></p>
<pre>
@@ -814,6 +821,120 @@ _FloatValue = rand:uniform(). % [0.0; 1.0[</pre>
See also
<seealso marker="stdlib:rand#seed_s-1">rand:seed_s/1</seealso>.
</p>
+ <p>
+ When using the state object from this function the
+ <seealso marker="stdlib:rand">rand</seealso> functions using it
+ may throw exception <c>low_entropy</c> in case the random generator
+ failed due to lack of secure "randomness".
+ </p>
+ <note>
+ <p>
+ The state returned from this function can not be used
+ to get a reproducable random sequence as from
+ the other
+ <seealso marker="stdlib:rand">rand</seealso>
+ functions,
+ since reproducability does not match cryptographically safe.
+ </p>
+ <p>
+ The only supported usage is to generate one distinct
+ random sequence from this start state.
+ </p>
+ </note>
+ </desc>
+ </func>
+
+ <func>
+ <name>rand_seed_alg(Alg) -> rand:state()</name>
+ <fsummary>Strong random number generation plugin state</fsummary>
+ <type>
+ <v>Alg = crypto | crypto_cache</v>
+ </type>
+ <desc>
+ <marker id="rand_seed_alg-1" />
+ <p>
+ Creates state object for
+ <seealso marker="stdlib:rand">random number generation</seealso>,
+ in order to generate cryptographically strong random numbers.
+ See also
+ <seealso marker="stdlib:rand#seed-1">rand:seed/1</seealso> and
+ <seealso marker="#rand_seed_alg_s-1">rand_seed_alg_s/1</seealso>.
+ </p>
+ <p>
+ When using the state object from this function the
+ <seealso marker="stdlib:rand">rand</seealso> functions using it
+ may throw exception <c>low_entropy</c> in case the random generator
+ failed due to lack of secure "randomness".
+ </p>
+ <p>
+ The cache size can be changed from its default value using the
+ <seealso marker="crypto_app">
+ crypto app's
+ </seealso> configuration parameter <c>rand_cache_size</c>.
+ </p>
+ <p><em>Example</em></p>
+ <pre>
+_ = crypto:rand_seed_alg(crypto_cache),
+_IntegerValue = rand:uniform(42), % [1; 42]
+_FloatValue = rand:uniform(). % [0.0; 1.0[</pre>
+ </desc>
+ </func>
+
+ <func>
+ <name>rand_seed_alg_s(Alg) -> rand:state()</name>
+ <fsummary>Strong random number generation plugin state</fsummary>
+ <type>
+ <v>Alg = crypto | crypto_cache</v>
+ </type>
+ <desc>
+ <marker id="rand_seed_alg_s-1" />
+ <p>
+ Creates state object for
+ <seealso marker="stdlib:rand">random number generation</seealso>,
+ in order to generate cryptographically strongly random numbers.
+ See also
+ <seealso marker="stdlib:rand#seed_s-1">rand:seed_s/1</seealso>.
+ </p>
+ <p>
+ If <c>Alg</c> is <c>crypto</c> this function behaves exactly like
+ <seealso marker="#rand_seed_s-0">rand_seed_s/0</seealso>.
+ </p>
+ <p>
+ If <c>Alg</c> is <c>crypto_cache</c> this function
+ fetches random data with OpenSSL's <c>RAND_bytes</c>
+ and caches it for speed using an internal word size
+ of 56 bits that makes calculations fast on 64 bit machines.
+ </p>
+ <p>
+ When using the state object from this function the
+ <seealso marker="stdlib:rand">rand</seealso> functions using it
+ may throw exception <c>low_entropy</c> in case the random generator
+ failed due to lack of secure "randomness".
+ </p>
+ <p>
+ The cache size can be changed from its default value using the
+ <seealso marker="crypto_app">
+ crypto app's
+ </seealso> configuration parameter <c>rand_cache_size</c>.
+ </p>
+ <note>
+ <p>
+ The state returned from this function can not be used
+ to get a reproducable random sequence as from
+ the other
+ <seealso marker="stdlib:rand">rand</seealso>
+ functions,
+ since reproducability does not match cryptographically safe.
+ </p>
+ <p>
+ In fact since random data is cached some numbers may
+ get reproduced if you try, but this is unpredictable.
+ </p>
+ <p>
+ The only supported usage is to generate one distinct
+ random sequence from this start state.
+ </p>
+ </note>
</desc>
</func>
diff --git a/lib/crypto/doc/src/crypto_app.xml b/lib/crypto/doc/src/crypto_app.xml
index ba22557480..8296b1bc77 100644
--- a/lib/crypto/doc/src/crypto_app.xml
+++ b/lib/crypto/doc/src/crypto_app.xml
@@ -68,6 +68,24 @@
thus the crypto module will fail to load. This mechanism
prevents the accidental use of non-validated algorithms.</p>
</item>
+ <tag><c>rand_cache_size = integer()</c></tag>
+ <item>
+ <p>
+ Sets the cache size in bytes to use by
+ <seealso marker="crypto#rand_seed_alg-1">
+ <c>crypto:rand_seed_alg(crypto_cache)</c>
+ </seealso> and
+ <seealso marker="crypto#rand_seed_alg_s-1">
+ <c>crypto:rand_seed_alg_s(crypto_cache)</c>
+ </seealso>.
+ This parameter is read when a seed function is called,
+ and then kept in generators state object. It has a rather
+ small default value that causes reads of strong random bytes
+ about once per hundred calls for a random value.
+ The set value is rounded up to an integral number of words
+ of the size these seed functions use.
+ </p>
+ </item>
</taglist>
</section>