Merge pull request #1573 from RaimoNiskanen/raimo/crypto/rand-cached

Rand plugin for cached strong crypto bytes
OTP-13370

5 files changed, 371 insertions, 188 deletions

diff --git a/lib/crypto/doc/src/crypto.xml b/lib/crypto/doc/src/crypto.xml
index 5b2c46a004..8c30d3d50c 100644
--- a/lib/crypto/doc/src/crypto.xml
+++ b/lib/crypto/doc/src/crypto.xml
@@ -753,9 +753,16 @@
 	  <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>
@@ -777,6 +784,120 @@ _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>
 
diff --git a/lib/crypto/src/crypto.app.src b/lib/crypto/src/crypto.app.src
index 1d3f35e465..492aa10e51 100644
--- a/lib/crypto/src/crypto.app.src
+++ b/lib/crypto/src/crypto.app.src
@@ -24,7 +24,7 @@
 	       crypto_ec_curves]},
     {registered, []},
     {applications, [kernel, stdlib]},
-    {env, [{fips_mode, false}]},
+    {env, [{fips_mode, false}, {rand_cache_size, 896}]},
     {runtime_dependencies, ["erts-9.0","stdlib-3.4","kernel-5.3"]}]}.
 
 
diff --git a/lib/crypto/src/crypto.erl b/lib/crypto/src/crypto.erl
index f9c4f7b71d..6b4f3a256d 100644
--- a/lib/crypto/src/crypto.erl
+++ b/lib/crypto/src/crypto.erl
@@ -30,11 +30,12 @@
 -export([hmac/3, hmac/4, hmac_init/2, hmac_update/2, hmac_final/1, hmac_final_n/2]).
 -export([cmac/3, cmac/4]).
 -export([exor/2, strong_rand_bytes/1, mod_pow/3]).
--export([rand_seed/0]).
--export([rand_seed_s/0]).
+-export([rand_seed/0, rand_seed_alg/1]).
+-export([rand_seed_s/0, rand_seed_alg_s/1]).
 -export([rand_plugin_next/1]).
 -export([rand_plugin_uniform/1]).
 -export([rand_plugin_uniform/2]).
+-export([rand_cache_plugin_next/1]).
 -export([rand_uniform/2]).
 -export([block_encrypt/3, block_decrypt/3, block_encrypt/4, block_decrypt/4]).
 -export([next_iv/2, next_iv/3]).
@@ -301,9 +302,17 @@ stream_decrypt(State, Data0) ->
 %%
 %% RAND - pseudo random numbers using RN_ and BN_ functions in crypto lib
 %%
+-type rand_cache_seed() ::
+        nonempty_improper_list(non_neg_integer(), binary()).
 -spec strong_rand_bytes(non_neg_integer()) -> binary().
 -spec rand_seed() -> rand:state().
 -spec rand_seed_s() -> rand:state().
+-spec rand_seed_alg(Alg :: atom()) ->
+                           {rand:alg_handler(),
+                            atom() | rand_cache_seed()}.
+-spec rand_seed_alg_s(Alg :: atom()) ->
+                             {rand:alg_handler(),
+                              atom() | rand_cache_seed()}.
 -spec rand_uniform(crypto_integer(), crypto_integer()) ->
 			  crypto_integer().
 
@@ -319,12 +328,36 @@ rand_seed() ->
     rand:seed(rand_seed_s()).
 
 rand_seed_s() ->
+    rand_seed_alg_s(?MODULE).
+
+rand_seed_alg(Alg) ->
+    rand:seed(rand_seed_alg_s(Alg)).
+
+-define(CRYPTO_CACHE_BITS, 56).
+rand_seed_alg_s(?MODULE) ->
     {#{ type => ?MODULE,
         bits => 64,
         next => fun ?MODULE:rand_plugin_next/1,
         uniform => fun ?MODULE:rand_plugin_uniform/1,
         uniform_n => fun ?MODULE:rand_plugin_uniform/2},
-     no_seed}.
+     no_seed};
+rand_seed_alg_s(crypto_cache) ->
+    CacheBits = ?CRYPTO_CACHE_BITS,
+    EnvCacheSize =
+        application:get_env(
+          crypto, rand_cache_size, CacheBits * 16), % Cache 16 * 8 words
+    Bytes = (CacheBits + 7) div 8,
+    CacheSize =
+        case ((EnvCacheSize + (Bytes - 1)) div Bytes) * Bytes of
+            Sz when is_integer(Sz), Bytes =< Sz ->
+                Sz;
+            _ ->
+                Bytes
+        end,
+    {#{ type => crypto_cache,
+        bits => CacheBits,
+        next => fun ?MODULE:rand_cache_plugin_next/1},
+     {CacheBits, CacheSize, <<>>}}.
 
 rand_plugin_next(Seed) ->
     {bytes_to_integer(strong_rand_range(1 bsl 64)), Seed}.
@@ -335,6 +368,12 @@ rand_plugin_uniform(State) ->
 rand_plugin_uniform(Max, State) ->
     {bytes_to_integer(strong_rand_range(Max)) + 1, State}.
 
+rand_cache_plugin_next({CacheBits, CacheSize, <<>>}) ->
+    rand_cache_plugin_next(
+      {CacheBits, CacheSize, strong_rand_bytes(CacheSize)});
+rand_cache_plugin_next({CacheBits, CacheSize, Cache}) ->
+    <<I:CacheBits, NewCache/binary>> = Cache,
+    {I, {CacheBits, CacheSize, NewCache}}.
 
 strong_rand_range(Range) when is_integer(Range), Range > 0 ->
     BinRange = int_to_bin(Range),
@@ -382,7 +421,7 @@ rand_uniform_nif(_From,_To) -> ?nif_stub.
 
 
 -spec rand_seed(binary()) -> ok.
-rand_seed(Seed) ->
+rand_seed(Seed) when is_binary(Seed) ->
     rand_seed_nif(Seed).
 
 rand_seed_nif(_Seed) -> ?nif_stub.
diff --git a/lib/stdlib/test/rand_SUITE.erl b/lib/stdlib/test/rand_SUITE.erl
index 432293b656..f69d42551e 100644
--- a/lib/stdlib/test/rand_SUITE.erl
+++ b/lib/stdlib/test/rand_SUITE.erl
@@ -80,7 +80,7 @@ test() ->
       end, Tests).
 
 algs() ->
-    [exs64, exsplus, exsp, exrop, exs1024, exs1024s].
+    [exrop, exsp, exs1024s, exs64, exsplus, exs1024].
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
@@ -459,213 +459,233 @@ measure(Config) ->
             {skip,{will_not_run_in_scaled_time,Scale}}
     end.
 
+-define(CHECK_UNIFORM_RANGE(Gen, Range, X, St),
+        case (Gen) of
+            {(X), (St)} when is_integer(X), 1 =< (X), (X) =< (Range) ->
+                St
+        end).
+-define(CHECK_UNIFORM(Gen, X, St),
+        case (Gen) of
+            {(X), (St)} when is_float(X), 0.0 =< (X), (X) < 1.0 ->
+                St
+        end).
+-define(CHECK_UNIFORM_NZ(Gen, X, St),
+        case (Gen) of
+            {(X), (St)} when is_float(X), 0.0 < (X), (X) =< 1.0 ->
+                St
+        end).
+-define(CHECK_NORMAL(Gen, X, St),
+        case (Gen) of
+            {(X), (St)} when is_float(X) ->
+                St
+        end).
+
 do_measure(_Config) ->
-    Algos =
+    Algs =
+        algs() ++
         try crypto:strong_rand_bytes(1) of
-            <<_>> -> [crypto64, crypto]
+            <<_>> -> [crypto64, crypto_cache, crypto]
         catch
             error:low_entropy -> [];
             error:undef -> []
-        end ++ algs(),
+        end,
     %%
-    ct:pal("RNG uniform integer performance~n",[]),
-    TMark1 =
+    ct:pal("~nRNG uniform integer range 10000 performance~n",[]),
+    _ =
         measure_1(
-          random,
           fun (_) -> 10000 end,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
-    _ =
-        [measure_1(
-           Algo,
-           fun (_) -> 10000 end,
-           TMark1,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
-    ct:pal("~nRNG uniform integer half range performance~n",[]),
-    HalfRangeFun = fun (State) -> half_range(State) end,
-    TMark2 =
-        measure_1(
-          random,
-          HalfRangeFun,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
+    ct:pal("~nRNG uniform integer 32 bit performance~n",[]),
     _ =
-        [measure_1(
-           Algo,
-           HalfRangeFun,
-           TMark2,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
-    %%
-    ct:pal("~nRNG uniform integer half range + 1  performance~n",[]),
-    HalfRangePlus1Fun = fun (State) -> half_range(State) + 1 end,
-    TMark3 =
         measure_1(
-          random,
-          HalfRangePlus1Fun,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
+          fun (_) -> 1 bsl 32 end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
+    %%
+    ct:pal("~nRNG uniform integer half range + 1 performance~n",[]),
     _ =
-        [measure_1(
-           Algo,
-           HalfRangePlus1Fun,
-           TMark3,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
+        measure_1(
+          fun (State) -> half_range(State) + 1 end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
     ct:pal("~nRNG uniform integer full range - 1 performance~n",[]),
-    FullRangeMinus1Fun = fun (State) -> (half_range(State) bsl 1) - 1 end,
-    TMark4 =
-        measure_1(
-          random,
-          FullRangeMinus1Fun,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
     _ =
-        [measure_1(
-           Algo,
-           FullRangeMinus1Fun,
-           TMark4,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
+        measure_1(
+          fun (State) -> (half_range(State) bsl 1) - 1 end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
     ct:pal("~nRNG uniform integer full range performance~n",[]),
-    FullRangeFun = fun (State) -> half_range(State) bsl 1 end,
-    TMark5 =
-        measure_1(
-          random,
-          FullRangeFun,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
     _ =
-        [measure_1(
-           Algo,
-           FullRangeFun,
-           TMark5,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
+        measure_1(
+          fun (State) -> half_range(State) bsl 1 end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
     ct:pal("~nRNG uniform integer full range + 1 performance~n",[]),
-    FullRangePlus1Fun = fun (State) -> (half_range(State) bsl 1) + 1 end,
-    TMark6 =
-        measure_1(
-          random,
-          FullRangePlus1Fun,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
     _ =
-        [measure_1(
-           Algo,
-           FullRangePlus1Fun,
-           TMark6,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
+        measure_1(
+          fun (State) -> (half_range(State) bsl 1) + 1 end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
     ct:pal("~nRNG uniform integer double range performance~n",[]),
-    DoubleRangeFun = fun (State) -> half_range(State) bsl 2 end,
-    TMark7 =
-        measure_1(
-          random,
-          DoubleRangeFun,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
     _ =
-        [measure_1(
-           Algo,
-           DoubleRangeFun,
-           TMark7,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
+        measure_1(
+          fun (State) ->
+                  half_range(State) bsl 2
+          end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
     ct:pal("~nRNG uniform integer double range + 1  performance~n",[]),
-    DoubleRangePlus1Fun = fun (State) -> (half_range(State) bsl 2) + 1 end,
-    TMark8 =
+    _ =
         measure_1(
-          random,
-          DoubleRangePlus1Fun,
-          undefined,
-          fun (Range, State) ->
-                  {int, random:uniform_s(Range, State)}
-          end),
+          fun (State) ->
+                  (half_range(State) bsl 2) + 1
+          end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
+    %%
+    ct:pal("~nRNG uniform integer 64 bit performance~n",[]),
     _ =
-        [measure_1(
-           Algo,
-           DoubleRangePlus1Fun,
-           TMark8,
-           fun (Range, State) ->
-                   {int, rand:uniform_s(Range, State)}
-           end) || Algo <- Algos],
+        measure_1(
+          fun (_) -> 1 bsl 64 end,
+          fun (State, Range, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM_RANGE(
+                               Mod:uniform_s(Range, St0), Range,
+                               X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
     ct:pal("~nRNG uniform float performance~n",[]),
-    TMark9 =
-        measure_1(
-          random,
+    _ = measure_1(
           fun (_) -> 0 end,
-          undefined,
-          fun (_, State) ->
-                  {uniform, random:uniform_s(State)}
-          end),
-    _ =
-        [measure_1(
-           Algo, 
-           fun (_) -> 0 end,
-           TMark9,
-           fun (_, State) ->
-                   {uniform, rand:uniform_s(State)}
-           end) || Algo <- Algos],
+          fun (State, _, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_UNIFORM(Mod:uniform_s(St0), X, St)
+                    end,
+                    State)
+          end,
+          Algs),
     %%
     ct:pal("~nRNG normal float performance~n",[]),
-    io:format("~.12w: not implemented (too few bits)~n", [random]),
-    _ = [measure_1(
-           Algo,
-           fun (_) -> 0 end,
-           TMark9,
-           fun (_, State) ->
-                   {normal, rand:normal_s(State)}
-           end) || Algo <- Algos],
+    _ = measure_1(
+          fun (_) -> 0 end,
+          fun (State, _, Mod) ->
+                  measure_loop(
+                    fun (St0) ->
+                            ?CHECK_NORMAL(Mod:normal_s(St0), X, St1)
+                    end,
+                    State)
+          end,
+          Algs),
     ok.
 
-measure_1(Algo, RangeFun, TMark, Gen) ->
+measure_loop(Fun, State) ->
+    measure_loop(Fun, State, ?LOOP).
+%%
+measure_loop(Fun, State, N) when 0 < N ->
+    measure_loop(Fun, Fun(State), N-1);
+measure_loop(_, _, _) ->
+    ok.
+
+measure_1(RangeFun, Fun, Algs) ->
+    TMark = measure_1(RangeFun, Fun, hd(Algs), undefined),
+    [TMark] ++
+        [measure_1(RangeFun, Fun, Alg, TMark) || Alg <- tl(Algs)].
+
+measure_1(RangeFun, Fun, Alg, TMark) ->
     Parent = self(),
-    Seed =
-        case Algo of
+    {Mod, State} =
+        case Alg of
             crypto64 ->
-                crypto64_seed();
+                {rand, crypto64_seed()};
+            crypto_cache ->
+                {rand, crypto:rand_seed_alg(crypto_cache)};
             crypto ->
-                crypto:rand_seed_s();
+                {rand, crypto:rand_seed_s()};
             random ->
-                random:seed(os:timestamp()), get(random_seed);
+                {random, random:seed(os:timestamp()), get(random_seed)};
             _ ->
-                rand:seed_s(Algo)
+                {rand, rand:seed_s(Alg)}
         end,
-    Range = RangeFun(Seed),
+    Range = RangeFun(State),
     Pid = spawn_link(
             fun() ->
-                    Fun = fun() -> measure_2(?LOOP, Range, Seed, Gen) end,
-                    {Time, ok} = timer:tc(Fun),
+                    {Time, ok} = timer:tc(fun () -> Fun(State, Range, Mod) end),
                     Percent =
                         case TMark of
                             undefined -> 100;
@@ -673,7 +693,7 @@ measure_1(Algo, RangeFun, TMark, Gen) ->
                         end,
                     io:format(
                       "~.12w: ~p ns ~p% [16#~.16b]~n",
-                      [Algo, (Time * 1000 + 500) div ?LOOP, Percent, Range]),
+                      [Alg, (Time * 1000 + 500) div ?LOOP, Percent, Range]),
                     Parent ! {self(), Time},
                     normal
             end),
@@ -681,21 +701,6 @@ measure_1(Algo, RangeFun, TMark, Gen) ->
 	{Pid, Msg} -> Msg
     end.
 
-measure_2(N, Range, State0, Fun) when N > 0 ->
-    case Fun(Range, State0) of
-	{int, {Random, State}}
-	  when is_integer(Random), Random >= 1, Random =< Range ->
-	    measure_2(N-1, Range, State, Fun);
-	{uniform, {Random, State}}
-          when is_float(Random), 0.0 =< Random, Random < 1.0 ->
-	    measure_2(N-1, Range, State, Fun);
-	{normal, {Random, State}} when is_float(Random) ->
-	    measure_2(N-1, Range, State, Fun);
-	Res ->
-	    exit({error, Res, State0})
-    end;
-measure_2(0, _, _, _) -> ok.
-
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% The jump sequence tests has two parts
 %% for those with the functional API (jump/1)