crypto
Crypto Functions
This module provides a set of cryptographic functions.

Hash functions 
Secure Hash Standard ,The MD5 Message Digest Algorithm (RFC 1321) andThe MD4 Message Digest Algorithm (RFC 1320) 
Hmac functions 
KeyedHashing for Message Authentication (RFC 2104) 
Block ciphers 
ECB, CBC, CFB, OFB and CTR 
RSA encryption RFC 1321 
Digital signatures
Digital Signature Standard (DSS) andElliptic Curve Digital Signature Algorithm (ECDSA) 
Secure Remote Password Protocol (SRP  RFC 2945)
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
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_private() = key_value()
Where is a
or b
from
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
dh_public() = key_value()
dh_private() = key_value()
dh_params() = [key_value()] = [P, G]
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_cbc128  aes_cfb8  aes_cfb128  aes_ige256  blowfish_cbc 
blowfish_cfb64  des_cbc  des_cfb  des3_cbc  des3_cbf
 des_ede3  rc2_cbc
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() = des_cbc  des_cfb  des3_cbc  des3_cbf  des_ede3 
blowfish_cbc  blowfish_cfb64  aes_cbc128  aes_cfb8  aes_cfb128 aes_cbc256  aes_ige256  rc2_cbc  aes_ctr 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.
Functions
block_encrypt(Type, Key, Ivec, PlainText) > CipherText
Type = block_cipher()
Key = block_key()
PlainText = iodata()
IVec = CipherText = binary()
Encrypt PlainText
according to Type
block cipher.
IVec
is an arbitrary initializing vector.
May throw exception notsup
in case the chosen Type
is not supported by the underlying OpenSSL implementation.
block_decrypt(Type, Key, Ivec, CipherText) > PlainText
Type = block_cipher()
Key = block_key()
PlainText = iodata()
IVec = CipherText = binary()
Decrypt CipherText
according to Type
block cipher.
IVec
is an arbitrary initializing vector.
May throw exception notsup
in case the chosen Type
is not supported by the underlying OpenSSL implementation.
bytes_to_integer(Bin) > Integer
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
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
Data1, Data2 = iodata()
Result = binary()
Performs bitwise XOR (exclusive or) on the data supplied.
generate_key(Type, Params) > {PublicKey, PrivKeyOut}
generate_key(Type, Params, PrivKeyIn) > {PublicKey, PrivKeyOut}
Type = dh  ecdh  srp
Params = dh_params()  ecdh_params()  SrpUserParams  SrpHostParams
SrpUserParams = {user, [Generator::binary(), Prime::binary(), Version::atom()]}
SrpHostParams = {host, [Verifier::binary(), Generator::binary(), Prime::binary(), Version::atom()]}
PublicKey = dh_public()  ecdh_public()  srp_public()
PrivKeyIn = undefined  dh_private()  srp_private()
PrivKeyOut = dh_private()  ecdh_private()  srp_private()
Generates public keys of type Type
.
See also public_key:generate_key/1
hash(Type, Data) > Digest
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
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
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
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
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
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
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
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
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.
info_lib() > [{Name,VerNum,VerStr}]
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">>,9469983,<<"OpenSSL 0.9.8a 11 Oct 2005">>}]
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
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
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
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
Type = rsa
PlainText = binary()
PrivateKey = rsa_private()
Padding = rsa_pkcs1_padding  rsa_no_padding
CipherText = binary()
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.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
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
Type = rsa
PlainText = binary()
PublicKey = rsa_public()
Padding = rsa_pkcs1_padding  rsa_pkcs1_oaep_padding  rsa_no_padding
CipherText = binary()
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.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_bytes(N) > binary()
N = integer()
Generates N bytes randomly uniform 0..255, and returns the
result in a binary. Uses the crypto
library pseudorandom
number generator.
rand_seed(Seed) > ok
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
stong_rand_bytes/1 returns low_entropy
rand_uniform(Lo, Hi) > N
Lo, Hi, N = integer()
Generate a random number N, Lo =< N < Hi.
Uses the
crypto
library pseudorandom number generator.
Hi
must be larger than Lo
.
sign(Algorithm, DigestType, Msg, Key) > binary()
Algorithm = rsa  dss  ecdsa
Msg = binary()  {digest,binary()}
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
.
start() > ok
Equivalent to application:start(crypto).
stop() > ok
Equivalent to application:stop(crypto).
strong_rand_bytes(N) > binary()
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".
stream_init(Type, Key) > State
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
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 bts 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}
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 }
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
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
EllipticCurveList = [ec_named_curve()]
Can be used to determine which named elliptic curves are supported.
ec_curve(NamedCurve) > EllipticCurve
NamedCurve = ec_named_curve()
EllipticCurve = ec_explicit_curve()
Return the defining parameters of a elliptic curve.
verify(Algorithm, DigestType, Msg, Signature, Key) > boolean()
Algorithm = rsa  dss  ecdsa
Msg = binary()  {digest,binary()}
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
.