crypto

Reference Manual

Version 4.0

Table of Contents

crypto

Module

crypto

Module Summary

Crypto Functions

Description

This module provides a set of cryptographic functions.

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 

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
 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 
 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.

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()
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]

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()
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()
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()
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()

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 = digest_type()
Key = rsa_private() | dss_private() | [ecdh_private(),ecdh_params()]

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()]}

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()

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 = digest_type()
Signature = binary()
Key = rsa_public() | dss_public() | [ecdh_public(),ecdh_params()]

Verifies a digital signature

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

See also public_key:verify/4.

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