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       crypto - The Crypto Application


       The  purpose  of  the  Crypto  application  is  to  provide an Erlang API to cryptographic
       functions, see crypto(3erl). Note that the API is on a fairly low level and there are some
       corresponding  API functions available in public_key(3erl), on a higher abstraction level,
       that uses the crypto application in its implementation.


       The current crypto implementation uses nifs to interface OpenSSLs crypto library  and  may
       work  with limited functionality with as old versions as OpenSSL 0.9.8c. FIPS mode support
       requires at least version 1.0.1 and a FIPS  capable  OpenSSL  installation.  We  recommend
       using  a  version  that  is  officially  supported  by the OpenSSL project. API compatible
       backends like LibreSSL should also work.

       Source releases of OpenSSL can be downloaded from the OpenSSL project home page, or mirror
       sites listed there.


       The  following  configuration  parameters  are  defined  for  the  crypto application. See
       app(3erl) for more information about configuration parameters.

         fips_mode = boolean():
           Specifies whether to run crypto in FIPS mode. This setting will take effect  when  the
           nif  module is loaded. If FIPS mode is requested but not available at run time the nif
           module and thus the crypto module will fail  to  load.  This  mechanism  prevents  the
           accidental use of non-validated algorithms.

         rand_cache_size = integer():
           Sets  the  cache  size  in  bytes  to  use  by  crypto:rand_seed_alg(crypto_cache) and
           crypto:rand_seed_alg_s(crypto_cache). 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.