diff options
Diffstat (limited to 'lib/crypto/doc/src/crypto.xml')
| -rw-r--r-- | lib/crypto/doc/src/crypto.xml | 114 |
1 files changed, 104 insertions, 10 deletions
diff --git a/lib/crypto/doc/src/crypto.xml b/lib/crypto/doc/src/crypto.xml index 651b647e1c..b8ec41bea8 100644 --- a/lib/crypto/doc/src/crypto.xml +++ b/lib/crypto/doc/src/crypto.xml @@ -1,4 +1,3 @@ -<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE erlref SYSTEM "erlref.dtd"> <erlref> @@ -1002,7 +1001,7 @@ _FloatValue = rand:uniform(). % [0.0; 1.0[</pre> </p> <note> <p> - The state returned from this function can not be used + The state returned from this function cannot be used to get a reproducable random sequence as from the other <seealso marker="stdlib:rand">rand</seealso> @@ -1028,7 +1027,8 @@ _FloatValue = rand:uniform(). % [0.0; 1.0[</pre> <p> Creates state object for <seealso marker="stdlib:rand">random number generation</seealso>, - in order to generate cryptographically strong random numbers. + in order to generate cryptographically strong random numbers, + and saves it in the process dictionary before returning it as well. 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>. @@ -1039,12 +1039,6 @@ _FloatValue = rand:uniform(). % [0.0; 1.0[</pre> may raise exception <c>error: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), @@ -1054,6 +1048,34 @@ _FloatValue = rand:uniform(). % [0.0; 1.0[</pre> </func> <func> + <name>rand_seed_alg(Alg, Seed) -> rand:state()</name> + <fsummary>Strong random number generation plugin state</fsummary> + <type> + <v>Alg = crypto_aes</v> + </type> + <desc> + <marker id="rand_seed_alg-2" /> + <p> + Creates a state object for + <seealso marker="stdlib:rand">random number generation</seealso>, + in order to generate cryptographically unpredictable random numbers, + and saves it in the process dictionary before returning it as well. + See also + <seealso marker="#rand_seed_alg_s-2">rand_seed_alg_s/2</seealso>. + </p> + <p><em>Example</em></p> + <pre> +_ = crypto:rand_seed_alg(crypto_aes, "my seed"), +IntegerValue = rand:uniform(42), % [1; 42] +FloatValue = rand:uniform(), % [0.0; 1.0[ +_ = crypto:rand_seed_alg(crypto_aes, "my seed"), +IntegerValue = rand:uniform(42), % Same values +FloatValue = rand:uniform(). % again + </pre> + </desc> + </func> + + <func> <name>rand_seed_alg_s(Alg) -> rand:state()</name> <fsummary>Strong random number generation plugin state</fsummary> <type> @@ -1090,9 +1112,15 @@ _FloatValue = rand:uniform(). % [0.0; 1.0[</pre> crypto app's </seealso> configuration parameter <c>rand_cache_size</c>. </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 + The state returned from this function cannot be used to get a reproducable random sequence as from the other <seealso marker="stdlib:rand">rand</seealso> @@ -1112,6 +1140,72 @@ _FloatValue = rand:uniform(). % [0.0; 1.0[</pre> </func> <func> + <name>rand_seed_alg_s(Alg, Seed) -> rand:state()</name> + <fsummary>Strong random number generation plugin state</fsummary> + <type> + <v>Alg = crypto_aes</v> + </type> + <desc> + <marker id="rand_seed_alg_s-2" /> + <p> + Creates a state object for + <seealso marker="stdlib:rand">random number generation</seealso>, + in order to generate cryptographically unpredictable random numbers. + See also + <seealso marker="#rand_seed_alg-1">rand_seed_alg/1</seealso>. + </p> + <p> + To get a long period the Xoroshiro928 generator from the + <seealso marker="stdlib:rand">rand</seealso> + module is used as a counter (with period 2^928 - 1) + and the generator states are scrambled through AES + to create 58-bit pseudo random values. + </p> + <p> + The result should be statistically completely unpredictable + random values, since the scrambling is cryptographically strong + and the period is ridiculously long. But the generated numbers + are not to be regarded as cryptographically strong since + there is no re-keying schedule. + </p> + <list type="bulleted"> + <item> + <p> + If you need cryptographically strong random numbers use + <seealso marker="#rand_seed_alg_s-1">rand_seed_alg_s/1</seealso> + with <c>Alg =:= crypto</c> or <c>Alg =:= crypto_cache</c>. + </p> + </item> + <item> + <p> + If you need to be able to repeat the sequence use this function. + </p> + </item> + <item> + <p> + If you do not need the statistical quality of this function, + there are faster algorithms in the + <seealso marker="stdlib:rand">rand</seealso> + module. + </p> + </item> + </list> + <p> + Thanks to the used generator the state object supports the + <seealso marker="stdlib:rand#jump-0"><c>rand:jump/0,1</c></seealso> + function with distance 2^512. + </p> + <p> + Numbers are generated in batches and cached for speed reasons. + 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> + </desc> + </func> + + <func> <name name="stream_init" arity="2"/> <fsummary></fsummary> <desc> |