crypto
Module
Module Summary
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  KeyedHashing for Message Authentication (RFC 2104)

Cmac functions  The AESCMAC Algorithm (RFC 4493)

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

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

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_(privatepublic)_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
Types
Encrypt PlainText according to Type block cipher.
May throw exception notsup in case the chosen Type is not supported by the underlying OpenSSL implementation.
Types
Decrypt CipherText according to Type block cipher.
May throw exception notsup in case the chosen Type is not supported by the underlying OpenSSL implementation.
Types
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.
Types
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.
Types
Convert binary representation, of an integer, to an Erlang integer.
Types
Computes the shared secret from the private key and the other party's public key. See also public_key:compute_key/2
Types
Performs bitwise XOR (exclusive or) on the data supplied.
Types
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.
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.
Types
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.
Types
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.
Types
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.
Types
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.
Types
Computes a HMAC of type Type from Data using Key as the authentication key.
MacLength will limit the size of the resultant Mac.
Types
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.
Types
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
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.
Types
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.
Types
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.
Types
Computes a CMAC of type Type from Data using Key as the authentication key.
MacLength will limit the size of the resultant Mac.
Types
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.
In FIPS mode all nonFIPS compliant algorithms are disabled and throw exception not_supported. Check supports that in FIPS mode returns the restricted list of available algorithms.
Types
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"">>}]
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.
Types
Computes the function N^P mod M.
Types
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.
Types
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]
Types
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.
Types
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]
Types
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]
Types
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]
Types
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
Types
Generate a random number N, Lo =< N < Hi. Uses the crypto library pseudorandom number generator. Hi must be larger than Lo.
Types
Creates a digital signature.
Algorithm dss can only be used together with digest type sha.
See also public_key:sign/3.
Equivalent to application:start(crypto).
Equivalent to application:stop(crypto).
Types
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".
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 in the process dictionary before returning it as well. See also rand:seed/1 and rand_seed_s/0.
When using the state object from this function the rand functions using it may throw exception low_entropy in case the random generator failed due to lack of secure "randomness".
Example
_ = crypto:rand_seed(), _IntegerValue = rand:uniform(42), % [1; 42] _FloatValue = rand:uniform(). % [0.0; 1.0[
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.
When using the state object from this function the rand functions using it may throw exception low_entropy in case the random generator failed due to lack of secure "randomness".
The state returned from this function can not be used to get a reproducable random sequence as from the other rand functions, since reproducability does not match cryptographically safe.
The only supported usage is to generate one distinct random sequence from this start state.
Types
Creates state object for random number generation, in order to generate cryptographically strong random numbers. See also rand:seed/1 and rand_seed_alg_s/1.
When using the state object from this function the rand functions using it may throw exception low_entropy in case the random generator failed due to lack of secure "randomness".
The cache size can be changed from its default value using the crypto app's configuration parameter rand_cache_size.
Example
_ = crypto:rand_seed_alg(crypto_cache), _IntegerValue = rand:uniform(42), % [1; 42] _FloatValue = rand:uniform(). % [0.0; 1.0[
Types
Creates state object for random number generation, in order to generate cryptographically strongly random numbers. See also rand:seed_s/1.
If Alg is crypto this function behaves exactly like rand_seed_s/0.
If Alg is crypto_cache this function fetches random data with OpenSSL's RAND_bytes and caches it for speed using an internal word size of 56 bits that makes calculations fast on 64 bit machines.
When using the state object from this function the rand functions using it may throw exception low_entropy in case the random generator failed due to lack of secure "randomness".
The cache size can be changed from its default value using the crypto app's configuration parameter rand_cache_size.
The state returned from this function can not be used to get a reproducable random sequence as from the other rand functions, since reproducability does not match cryptographically safe.
In fact since random data is cached some numbers may get reproduced if you try, but this is unpredictable.
The only supported usage is to generate one distinct random sequence from this start state.
Types
Initializes the state for use in RC4 stream encryption stream_encrypt and stream_decrypt
Types
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.
Types
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.
Types
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.
Types
Can be used to determine which crypto algorithms that are supported by the underlying OpenSSL library
Types
Can be used to determine which named elliptic curves are supported.
Types
Return the defining parameters of a elliptic curve.
Types
Verifies a digital signature
Algorithm dss can only be used together with digest type sha.
See also public_key:verify/4.
Types
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.
Types
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.
Types
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.
Types
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.
Types
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.
Types
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.
Types
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.