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NAME

       crypto - Crypto Functions

DESCRIPTION

       This module provides a set of cryptographic functions.

         * Hash  functions  -   Secure  Hash  Standard,  The MD5 Message Digest Algorithm (RFC 1321) and The MD4
           Message Digest Algorithm (RFC 1320)

         * Hmac functions -  Keyed-Hashing for Message Authentication (RFC 2104)

         * Cmac functions - The AES-CMAC Algorithm (RFC 4493)

         * Block ciphers - DES and AES in Block Cipher Modes -  ECB, CBC, CFB, OFB, CTR and GCM

         *
            RSA encryption RFC 1321

         * Digital signatures Digital Signature Standard (DSS) and Elliptic Curve  Digital  Signature  Algorithm
           (ECDSA)

         *
            Secure Remote Password Protocol (SRP - RFC 2945)

         * gcm:  Dworkin, M., "Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and
           GMAC", National Institute of Standards and Technology SP 800- 38D, November 2007.

DATA TYPES

       key_value() = integer() | binary()

       Always binary() when used as return value

       rsa_public() = [key_value()] = [E, N]

       Where E is the public exponent and N is public modulus.

       rsa_private() = [key_value()] = [E, N, D] | [E, N, D, P1, P2, E1, E2, C]

       Where E is the public exponent, N is public modulus and D is the private exponent. The longer key  format
       contains  redundant  information  that will make the calculation faster. P1,P2 are first and second prime
       factors. E1,E2 are first and second exponents. C is the CRT coefficient. Terminology is taken  from   RFC
       3447.

       dss_public() = [key_value()] = [P, Q, G, Y]

       Where P, Q and G are the dss parameters and Y is the public key.

       dss_private() = [key_value()] = [P, Q, G, X]

       Where P, Q and G are the dss parameters and X is the private key.

       srp_public() = key_value()

       Where is A or B from SRP design

       srp_private() = key_value()

       Where is a or b from SRP design

       Where Verifier is v, Generator is g and Prime is N, DerivedKey is X, and Scrambler is u (optional will be
       generated if not provided) from SRP design Version = '3' | '6' | '6a'

       dh_public() = key_value()

       dh_private() = key_value()

       dh_params() = [key_value()] = [P, G] | [P, G, PrivateKeyBitLength]

       ecdh_public() = key_value()

       ecdh_private() = key_value()

       ecdh_params() = ec_named_curve() | ec_explicit_curve()

       ec_explicit_curve() =
           {ec_field(), Prime :: key_value(), Point :: key_value(), Order :: integer(),
            CoFactor :: none | integer()}

       ec_field() = {prime_field, Prime :: integer()} |
           {characteristic_two_field, M :: integer(), Basis :: ec_basis()}

       ec_basis() = {tpbasis, K :: non_neg_integer()} |
           {ppbasis, K1 :: non_neg_integer(), K2 :: non_neg_integer(), K3 :: non_neg_integer()} |
           onbasis

       ec_named_curve() ->
             sect571r1| sect571k1| sect409r1| sect409k1| secp521r1| secp384r1| secp224r1| secp224k1|
             secp192k1| secp160r2| secp128r2| secp128r1| sect233r1| sect233k1| sect193r2| sect193r1|
             sect131r2| sect131r1| sect283r1| sect283k1| sect163r2| secp256k1| secp160k1| secp160r1|
             secp112r2| secp112r1| sect113r2| sect113r1| sect239k1| sect163r1| sect163k1| secp256r1|
             secp192r1|
             brainpoolP160r1| brainpoolP160t1| brainpoolP192r1| brainpoolP192t1| brainpoolP224r1|
             brainpoolP224t1| brainpoolP256r1| brainpoolP256t1| brainpoolP320r1| brainpoolP320t1|
             brainpoolP384r1| brainpoolP384t1| brainpoolP512r1| brainpoolP512t1

       Note that the sect curves are GF2m (characteristic two) curves and are only supported if  the  underlying
       OpenSSL has support for them. See also crypto:supports/0

       engine_key_ref() = #{engine   := engine_ref(),
                                      key_id   := key_id(),
                                      password => password()}

       engine_ref() = term()

       The result of a call to engine_load/3.

       key_id() = string() | binary()

       Identifies  the  key  to  be  used.  The  format  depends  on  the  loaded  engine.  It  is passed to the
       ENGINE_load_(private|public)_key functions in libcrypto.

       password() = string() | binary()

       The key's password

       stream_cipher() = rc4 | aes_ctr

       block_cipher() = aes_cbc | aes_cfb8 | aes_cfb128 | aes_ige256 | blowfish_cbc |
            blowfish_cfb64 | des_cbc | des_cfb | des3_cbc | des3_cfb | des_ede3 | rc2_cbc

       aead_cipher() = aes_gcm | chacha20_poly1305

       stream_key() = aes_key() | rc4_key()

       block_key() = aes_key() |  blowfish_key() | des_key()| des3_key()

       aes_key() = iodata()

       Key length is 128, 192 or 256 bits

       rc4_key() = iodata()

       Variable key length from 8 bits up to 2048 bits (usually between 40 and 256)

       blowfish_key() = iodata()

       Variable key length from 32 bits up to 448 bits

       des_key() = iodata()

       Key length is 64 bits (in CBC mode only 8 bits are used)

       des3_key() = [binary(), binary(), binary()]

       Each key part is 64 bits (in CBC mode only 8 bits are used)

       digest_type() =  md5 | sha | sha224 | sha256 | sha384 | sha512

       rsa_digest_type() = md5 | ripemd160 | sha | sha224 | sha256 | sha384 | sha512

       dss_digest_type() = sha | sha224 | sha256 | sha384 | sha512

       Note that the actual supported dss_digest_type depends on  the  underlying  crypto  library.  In  OpenSSL
       version  >=  1.0.1  the  listed  digest  are  supported,  while  in 1.0.0 only sha, sha224 and sha256 are
       supported. In version 0.9.8 only sha is supported.

       ecdsa_digest_type() = sha | sha224 | sha256 | sha384 | sha512

       sign_options() = [{rsa_pad, rsa_sign_padding()} | {rsa_pss_saltlen, integer()}]

       rsa_sign_padding() = rsa_pkcs1_padding | rsa_pkcs1_pss_padding

        hash_algorithms() =  md5 | ripemd160 | sha | sha224 | sha256 | sha384 | sha512

       md4 is also supported for hash_init/1 and hash/2. Note that both md4 and md5  are  recommended  only  for
       compatibility with existing applications.

        cipher_algorithms() = aes_cbc | aes_cfb8 | aes_cfb128 | aes_ctr | aes_gcm |
            aes_ige256 | blowfish_cbc | blowfish_cfb64 | chacha20_poly1305 | des_cbc |
            des_cfb | des3_cbc | des3_cfb | des_ede3 | rc2_cbc | rc4

        mac_algorithms() = hmac | cmac

        public_key_algorithms() = rsa |dss | ecdsa | dh | ecdh | ec_gf2m

       Note  that ec_gf2m is not strictly a public key algorithm, but a restriction on what curves are supported
       with ecdsa and ecdh.

       engine_method_type() = engine_method_rsa | engine_method_dsa | engine_method_dh |
            engine_method_rand | engine_method_ecdh | engine_method_ecdsa |
            engine_method_ciphers | engine_method_digests | engine_method_store |
            engine_method_pkey_meths | engine_method_pkey_asn1_meths

EXPORTS

       block_encrypt(Type, Key, PlainText) -> CipherText

              Types:

                 Type = des_ecb | blowfish_ecb | aes_ecb
                 Key = block_key()
                 PlainText = iodata()

              Encrypt PlainText according to Type block cipher.

              May throw exception notsup in case the chosen Type is not  supported  by  the  underlying  OpenSSL
              implementation.

       block_decrypt(Type, Key, CipherText) -> PlainText

              Types:

                 Type = des_ecb | blowfish_ecb | aes_ecb
                 Key = block_key()
                 PlainText = iodata()

              Decrypt CipherText according to Type block cipher.

              May  throw  exception  notsup  in  case the chosen Type is not supported by the underlying OpenSSL
              implementation.

       block_encrypt(Type, Key, Ivec, PlainText) -> CipherText
       block_encrypt(AeadType, Key, Ivec, {AAD, PlainText}) -> {CipherText, CipherTag}
       block_encrypt(aes_gcm, Key, Ivec, {AAD, PlainText, TagLength}) -> {CipherText, CipherTag}

              Types:

                 Type = block_cipher()
                 AeadType = aead_cipher()
                 Key = block_key()
                 PlainText = iodata()
                 AAD = IVec = CipherText = CipherTag = binary()
                 TagLength = 1..16

              Encrypt PlainText according to Type block cipher. IVec is an arbitrary initializing vector.

              In AEAD (Authenticated Encryption with Associated Data) mode, encrypt PlainTextaccording  to  Type
              block  cipher  and  calculate  CipherTag that also authenticates the AAD (Associated Authenticated
              Data).

              May throw exception notsup in case the chosen Type is not  supported  by  the  underlying  OpenSSL
              implementation.

       block_decrypt(Type, Key, Ivec, CipherText) -> PlainText
       block_decrypt(AeadType, Key, Ivec, {AAD, CipherText, CipherTag}) -> PlainText | error

              Types:

                 Type = block_cipher()
                 AeadType = aead_cipher()
                 Key = block_key()
                 PlainText = iodata()
                 AAD = IVec = CipherText = CipherTag = binary()

              Decrypt CipherText according to Type block cipher. IVec is an arbitrary initializing vector.

              In  AEAD (Authenticated Encryption with Associated Data) mode, decrypt CipherTextaccording to Type
              block cipher and check the authenticity the PlainText  and  AAD  (Associated  Authenticated  Data)
              using the CipherTag. May return error if the decryption or validation fail's

              May  throw  exception  notsup  in  case the chosen Type is not supported by the underlying OpenSSL
              implementation.

       bytes_to_integer(Bin) -> Integer

              Types:

                 Bin = binary() - as returned by crypto functions
                 Integer = integer()

              Convert binary representation, of an integer, to an Erlang integer.

       compute_key(Type, OthersPublicKey, MyKey, Params) -> SharedSecret

              Types:

                  Type = dh | ecdh | srp
                 OthersPublicKey = dh_public() | ecdh_public() | srp_public()
                 MyKey = dh_private() | ecdh_private() | {srp_public(),srp_private()}
                 Params = dh_params() | ecdh_params() | SrpUserParams | SrpHostParams
                 SrpUserParams   =   {user,   [DerivedKey::binary(),    Prime::binary(),    Generator::binary(),
                 Version::atom() | [Scrambler:binary()]]}
                 SrpHostParams    =    {host,    [Verifier::binary(),    Prime::binary(),    Version::atom()   |
                 [Scrambler::binary]]}
                 SharedSecret = binary()

              Computes the shared secret from the private key  and  the  other  party's  public  key.  See  also
              public_key:compute_key/2

       exor(Data1, Data2) -> Result

              Types:

                 Data1, Data2 = iodata()
                 Result = binary()

              Performs bit-wise XOR (exclusive or) on the data supplied.

       generate_key(Type, Params) -> {PublicKey, PrivKeyOut}
       generate_key(Type, Params, PrivKeyIn) -> {PublicKey, PrivKeyOut}

              Types:

                  Type = dh | ecdh | rsa | srp
                 Params = dh_params() | ecdh_params() | RsaParams | SrpUserParams | SrpHostParams
                 RsaParams = {ModulusSizeInBits::integer(), PublicExponent::key_value()}
                 SrpUserParams = {user, [Generator::binary(), Prime::binary(), Version::atom()]}
                 SrpHostParams    =    {host,    [Verifier::binary(),    Generator::binary(),   Prime::binary(),
                 Version::atom()]}
                 PublicKey = dh_public() | ecdh_public() | rsa_public() | srp_public()
                 PrivKeyIn = undefined | dh_private() | ecdh_private() | srp_private()
                 PrivKeyOut = dh_private() | ecdh_private() | rsa_private() | srp_private()

              Generates a public key of type Type. See also public_key:generate_key/1. May  throw  exception  an
              exception of class error:

                * badarg: an argument is of wrong type or has an illegal value,

                * low_entropy: the random generator failed due to lack of secure "randomness",

                * computation_failed: the computation fails of another reason than low_entropy.

          Note:
              RSA  key  generation  is  only  available  if  the runtime was built with dirty scheduler support.
              Otherwise, attempting to generate an RSA key will throw exception error:notsup.

       hash(Type, Data) -> Digest

              Types:

                 Type = md4 | hash_algorithms()
                 Data = iodata()
                 Digest = binary()

              Computes a message digest of type Type from Data.

              May throw exception notsup in case the chosen Type is not  supported  by  the  underlying  OpenSSL
              implementation.

       hash_init(Type) -> Context

              Types:

                 Type = md4 | hash_algorithms()

              Initializes  the  context  for streaming hash operations. Type determines which digest to use. The
              returned context should be used as argument to hash_update.

              May throw exception notsup in case the chosen Type is not  supported  by  the  underlying  OpenSSL
              implementation.

       hash_update(Context, Data) -> NewContext

              Types:

                 Data = iodata()

              Updates  the  digest represented by Context using the given Data. Context must have been generated
              using hash_init or a previous call to this function. Data can be any length.  NewContext  must  be
              passed into the next call to hash_update or hash_final.

       hash_final(Context) -> Digest

              Types:

                 Digest = binary()

              Finalizes  the  hash operation referenced by Context returned from a previous call to hash_update.
              The size of Digest is determined by the type of hash function used to generate it.

       hmac(Type, Key, Data) -> Mac
       hmac(Type, Key, Data, MacLength) -> Mac

              Types:

                 Type = hash_algorithms() - except ripemd160
                 Key = iodata()
                 Data = iodata()
                 MacLength = integer()
                 Mac = binary()

              Computes a HMAC of type Type from Data using Key as the authentication key.

              MacLength will limit the size of the resultant Mac.

       hmac_init(Type, Key) -> Context

              Types:

                 Type = hash_algorithms() - except ripemd160
                 Key = iodata()
                 Context = binary()

              Initializes the context for streaming HMAC operations. Type determines which hash function to  use
              in the HMAC operation. Key is the authentication key. The key can be any length.

       hmac_update(Context, Data) -> NewContext

              Types:

                 Context = NewContext = binary()
                 Data = iodata()

              Updates  the  HMAC  represented  by Context using the given Data. Context must have been generated
              using an HMAC init function (such as hmac_init). Data can be any length. NewContext must be passed
              into the next call to hmac_update or to one of the functions hmac_final and hmac_final_n

          Warning:
              Do not use a Context as argument in more than one call to hmac_update or hmac_final. The semantics
              of reusing old contexts in any way is undefined and could even crash the VM in  earlier  releases.
              The reason for this limitation is a lack of support in the underlying OpenSSL API.

       hmac_final(Context) -> Mac

              Types:

                 Context = Mac = binary()

              Finalizes the HMAC operation referenced by Context. The size of the resultant MAC is determined by
              the type of hash function used to generate it.

       hmac_final_n(Context, HashLen) -> Mac

              Types:

                 Context = Mac = binary()
                 HashLen = non_neg_integer()

              Finalizes the HMAC operation referenced by Context. HashLen must be greater than zero. Mac will be
              a  binary  with  at  most HashLen bytes. Note that if HashLen is greater than the actual number of
              bytes returned from the underlying hash, the returned hash will have fewer than HashLen bytes.

       cmac(Type, Key, Data) -> Mac
       cmac(Type, Key, Data, MacLength) -> Mac

              Types:

                 Type = block_cipher()
                 Key = iodata()
                 Data = iodata()
                 MacLength = integer()
                 Mac = binary()

              Computes a CMAC of type Type from Data using Key as the authentication key.

              MacLength will limit the size of the resultant Mac.

       info_fips() -> Status

              Types:

                 Status = enabled | not_enabled | not_supported

              Provides information about the FIPS operating status of crypto and the underlying OpenSSL library.
              If  crypto  was  built with FIPS support this can be either enabled (when running in FIPS mode) or
              not_enabled. For other builds this value is always not_supported.

          Warning:
              In FIPS mode all non-FIPS compliant algorithms are disabled  and  throw  exception  not_supported.
              Check supports that in FIPS mode returns the restricted list of available algorithms.

       info_lib() -> [{Name,VerNum,VerStr}]

              Types:

                 Name = binary()
                 VerNum = integer()
                 VerStr = binary()

              Provides the name and version of the libraries used by crypto.

              Name  is  the  name  of  the library. VerNum is the numeric version according to the library's own
              versioning scheme. VerStr contains a text variant of the version.

              > info_lib().
              [{<<"OpenSSL">>,269484095,<<"OpenSSL 1.1.0c  10 Nov 2016"">>}]

          Note:
              From  OTP  R16  the  numeric  version  represents  the  version  of  the  OpenSSL   header   files
              (openssl/opensslv.h)  used  when  crypto  was  compiled.  The  text variant represents the OpenSSL
              library used at runtime. In earlier OTP versions both numeric and text was taken from the library.

       mod_pow(N, P, M) -> Result

              Types:

                 N, P, M = binary() | integer()
                 Result = binary() | error

              Computes the function N^P mod M.

       next_iv(Type, Data) -> NextIVec
       next_iv(Type, Data, IVec) -> NextIVec

              Types:

                 Type = des_cbc | des3_cbc | aes_cbc | des_cfb
                 Data = iodata()
                 IVec = NextIVec = binary()

              Returns the initialization vector to be used in the next  iteration  of  encrypt/decrypt  of  type
              Type.  Data  is  the  encrypted  data  from the previous iteration step. The IVec argument is only
              needed for des_cfb as the vector used in the previous iteration step.

       private_decrypt(Type, CipherText, PrivateKey, Padding) -> PlainText

              Types:

                 Type = rsa
                 CipherText = binary()
                 PrivateKey = rsa_private() | engine_key_ref()
                 Padding = rsa_pkcs1_padding | rsa_pkcs1_oaep_padding | rsa_no_padding
                 PlainText = binary()

              Decrypts the CipherText, encrypted  with  public_encrypt/4  (or  equivalent  function)  using  the
              PrivateKey, and returns the plaintext (message digest). This is a low level signature verification
              operation  used   for   instance   by   older   versions   of   the   SSL   protocol.   See   also
              public_key:decrypt_private/[2,3]

       privkey_to_pubkey(Type, EnginePrivateKeyRef) -> PublicKey

              Types:

                 Type = rsa | dss
                 EnginePrivateKeyRef = engine_key_ref()
                 PublicKey = rsa_public() | dss_public()

              Fetches  the  corresponding  public key from a private key stored in an Engine. The key must be of
              the type indicated by the Type parameter.

       private_encrypt(Type, PlainText, PrivateKey, Padding) -> CipherText

              Types:

                 Type = rsa
                 PlainText = binary()
                    The size of the PlainText must be less than byte_size(N)-11 if  rsa_pkcs1_padding  is  used,
                   and byte_size(N) if rsa_no_padding is used, where N is public modulus of the RSA key.
                 PrivateKey = rsa_private() | engine_key_ref()
                 Padding = rsa_pkcs1_padding | rsa_no_padding
                 CipherText = binary()

              Encrypts  the  PlainText  using  the  PrivateKey  and  returns the ciphertext. This is a low level
              signature  operation  used  for  instance  by  older  versions  of  the  SSL  protocol.  See  also
              public_key:encrypt_private/[2,3]

       public_decrypt(Type, CipherText, PublicKey, Padding) -> PlainText

              Types:

                 Type = rsa
                 CipherText = binary()
                 PublicKey = rsa_public() | engine_key_ref()
                 Padding = rsa_pkcs1_padding | rsa_no_padding
                 PlainText = binary()

              Decrypts  the  CipherText,  encrypted  with  private_encrypt/4(or  equivalent  function) using the
              PrivateKey, and returns the plaintext (message digest). This is a low level signature verification
              operation   used   for   instance   by   older   versions   of   the   SSL   protocol.   See  also
              public_key:decrypt_public/[2,3]

       public_encrypt(Type, PlainText, PublicKey, Padding) -> CipherText

              Types:

                 Type = rsa
                 PlainText = binary()
                    The size of the PlainText must be less than byte_size(N)-11 if  rsa_pkcs1_padding  is  used,
                   and byte_size(N) if rsa_no_padding is used, where N is public modulus of the RSA key.
                 PublicKey = rsa_public() | engine_key_ref()
                 Padding = rsa_pkcs1_padding | rsa_pkcs1_oaep_padding | rsa_no_padding
                 CipherText = binary()

              Encrypts  the PlainText (message digest) using the PublicKey and returns the CipherText. This is a
              low level signature operation used for instance by older versions of the SSL  protocol.  See  also
              public_key:encrypt_public/[2,3]

       rand_seed(Seed) -> ok

              Types:

                 Seed = binary()

              Set  the  seed  for PRNG to the given binary. This calls the RAND_seed function from openssl. Only
              use this if the system you are running on does not have enough  "randomness"  built  in.  Normally
              this is when strong_rand_bytes/1 throws low_entropy

       rand_uniform(Lo, Hi) -> N

              Types:

                 Lo, Hi, N = integer()

              Generate  a random number N, Lo =< N < Hi. Uses the crypto library pseudo-random number generator.
              Hi must be larger than Lo.

       sign(Algorithm, DigestType, Msg, Key) -> binary()
       sign(Algorithm, DigestType, Msg, Key, Options) -> binary()

              Types:

                 Algorithm = rsa | dss | ecdsa
                 Msg = binary() | {digest,binary()}
                   The msg is either the binary "cleartext" data to be signed or  it  is  the  hashed  value  of
                   "cleartext" i.e. the digest (plaintext).
                 DigestType = rsa_digest_type() | dss_digest_type() | ecdsa_digest_type()
                 Key = rsa_private() | dss_private() | [ecdh_private(),ecdh_params()] | engine_key_ref()
                 Options = sign_options()

              Creates a digital signature.

              Algorithm dss can only be used together with digest type sha.

              See also public_key:sign/3.

       start() -> ok

              Equivalent to application:start(crypto).

       stop() -> ok

              Equivalent to application:stop(crypto).

       strong_rand_bytes(N) -> binary()

              Types:

                 N = integer()

              Generates  N  bytes  randomly  uniform  0..255,  and  returns  the  result  in  a  binary.  Uses a
              cryptographically secure prng  seeded  and  periodically  mixed  with  operating  system  provided
              entropy. By default this is the RAND_bytes method from OpenSSL.

              May  throw  exception  low_entropy  in  case  the  random  generator  failed due to lack of secure
              "randomness".

       rand_seed() -> rand:state()

              Creates state object for random number generation, in order to generate  cryptographically  strong
              random  numbers  (based  on  OpenSSL's  BN_rand_range),  and saves it on process dictionary before
              returning it as well. See also rand:seed/1.

              Example

              _ = crypto:rand_seed(),
              _IntegerValue = rand:uniform(42), % [1; 42]
              _FloatValue = rand:uniform().     % [0.0; 1.0[

       rand_seed_s() -> rand:state()

              Creates state object for random number generation, in order to generate cryptographically strongly
              random numbers (based on OpenSSL's BN_rand_range). See also rand:seed_s/1.

       stream_init(Type, Key) -> State

              Types:

                 Type = rc4
                 State = opaque()
                 Key = iodata()

              Initializes the state for use in RC4 stream encryption stream_encrypt and stream_decrypt

       stream_init(Type, Key, IVec) -> State

              Types:

                 Type = aes_ctr
                 State = opaque()
                 Key = iodata()
                 IVec = binary()

              Initializes the state for use in streaming AES encryption using Counter mode (CTR). Key is the AES
              key and must be either 128, 192, or 256 bits long. IVec is an arbitrary initializing vector of 128
              bits (16 bytes). This state is for use with stream_encrypt and stream_decrypt.

       stream_encrypt(State, PlainText) -> { NewState, CipherText}

              Types:

                 Text = iodata()
                 CipherText = binary()

              Encrypts PlainText according to the stream cipher Type specified in stream_init/3. Text can be any
              number of bytes. The initial State is created using stream_init. NewState must be passed into  the
              next call to stream_encrypt.

       stream_decrypt(State, CipherText) -> { NewState, PlainText }

              Types:

                 CipherText = iodata()
                 PlainText = binary()

              Decrypts  CipherText according to the stream cipher Type specified in stream_init/3. PlainText can
              be any number of bytes. The initial State is created using stream_init. NewState  must  be  passed
              into the next call to stream_decrypt.

       supports() -> AlgorithmList

              Types:

                  AlgorithmList = [{hashs, [hash_algorithms()]}, {ciphers, [cipher_algorithms()]}, {public_keys,
                 [public_key_algorithms()]}, {macs, [mac_algorithms()]}]

              Can be used to determine which crypto algorithms that are  supported  by  the  underlying  OpenSSL
              library

       ec_curves() -> EllipticCurveList

              Types:

                 EllipticCurveList = [ec_named_curve()]

              Can be used to determine which named elliptic curves are supported.

       ec_curve(NamedCurve) -> EllipticCurve

              Types:

                 NamedCurve = ec_named_curve()
                 EllipticCurve = ec_explicit_curve()

              Return the defining parameters of a elliptic curve.

       verify(Algorithm, DigestType, Msg, Signature, Key) -> boolean()
       verify(Algorithm, DigestType, Msg, Signature, Key, Options) -> boolean()

              Types:

                  Algorithm = rsa | dss | ecdsa
                 Msg = binary() | {digest,binary()}
                   The  msg  is either the binary "cleartext" data or it is the hashed value of "cleartext" i.e.
                   the digest (plaintext).
                 DigestType = rsa_digest_type() | dss_digest_type() | ecdsa_digest_type()
                 Signature = binary()
                 Key = rsa_public() | dss_public() | [ecdh_public(),ecdh_params()] | engine_key_ref()
                 Options = sign_options()

              Verifies a digital signature

              Algorithm dss can only be used together with digest type sha.

              See also public_key:verify/4.

       engine_get_all_methods() -> Result

              Types:

                 Result = [EngineMethod::atom()]

              Returns a list of all possible engine methods.

              May throw exception notsup  in  case  there  is  no  engine  support  in  the  underlying  OpenSSL
              implementation.

              See also the chapter Engine Load in the User's Guide.

       engine_load(EngineId, PreCmds, PostCmds) -> Result

              Types:

                 EngineId = unicode:chardata()
                 PreCmds, PostCmds = [{unicode:chardata(), unicode:chardata()}]
                 Result = {ok, Engine::term()} | {error, Reason::term()}

              Loads  the  OpenSSL  engine given by EngineId if it is available and then returns ok and an engine
              handle. This function is the same as calling engine_load/4 with EngineMethods set to a list of all
              the possible methods. An error tuple is returned if the engine can't be loaded.

              The  function  throws  a  badarg  if  the  parameters  are  in wrong format. It may also throw the
              exception notsup in case there is no engine support in the underlying OpenSSL implementation.

              See also the chapter Engine Load in the User's Guide.

       engine_load(EngineId, PreCmds, PostCmds, EngineMethods) -> Result

              Types:

                 EngineId = unicode:chardata()
                 PreCmds, PostCmds = [{unicode:chardata(), unicode:chardata()}]
                 EngineMethods = [engine_method_type()]
                 Result = {ok, Engine::term()} | {error, Reason::term()}

              Loads the OpenSSL engine given by EngineId if it is available and then returns ok  and  an  engine
              handle. An error tuple is returned if the engine can't be loaded.

              The  function  throws  a  badarg  if  the  parameters  are  in wrong format. It may also throw the
              exception notsup in case there is no engine support in the underlying OpenSSL implementation.

              See also the chapter Engine Load in the User's Guide.

       engine_unload(Engine) -> Result

              Types:

                 Engine = term()
                 Result = ok | {error, Reason::term()}

              Unloads the OpenSSL engine given by EngineId. An error tuple is returned if the  engine  can't  be
              unloaded.

              The  function throws a badarg if the parameter is in wrong format. It may also throw the exception
              notsup in case there is no engine support in the underlying OpenSSL implementation.

              See also the chapter Engine Load in the User's Guide.

       engine_list() -> Result

              Types:

                 Result = [EngineId::unicode:chardata()]

              List the id's of all engines in OpenSSL's internal list.

              It may also throw the exception notsup in case there  is  no  engine  support  in  the  underlying
              OpenSSL implementation.

              See also the chapter Engine Load in the User's Guide.

       engine_ctrl_cmd_string(Engine, CmdName, CmdArg) -> Result

              Types:

                 Engine = term()
                 CmdName = unicode:chardata()
                 CmdArg = unicode:chardata()
                 Result = ok | {error, Reason::term()}

              Sends  ctrl  commands  to the OpenSSL engine given by Engine. This function is the same as calling
              engine_ctrl_cmd_string/4 with Optional set to false.

              The function throws a badarg if the parameters  are  in  wrong  format.  It  may  also  throw  the
              exception notsup in case there is no engine support in the underlying OpenSSL implementation.

       engine_ctrl_cmd_string(Engine, CmdName, CmdArg, Optional) -> Result

              Types:

                 Engine = term()
                 CmdName = unicode:chardata()
                 CmdArg = unicode:chardata()
                 Optional = boolean()
                 Result = ok | {error, Reason::term()}

              Sends ctrl commands to the OpenSSL engine given by Engine. Optional is a boolean argument that can
              relax the semantics of the function. If set to true it will only  return  failure  if  the  ENGINE
              supported  the given command name but failed while executing it, if the ENGINE doesn't support the
              command name it will simply return success without doing anything. In this case we assume the user
              is only supplying commands specific to the given ENGINE so we set this to false.

              The  function  throws  a  badarg  if  the  parameters  are  in wrong format. It may also throw the
              exception notsup in case there is no engine support in the underlying OpenSSL implementation.