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crypto Crypto Functions

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)

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]

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

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() = des_cbc | des_cfb | des3_cbc | des3_cbf | des_ede3 | blowfish_cbc | blowfish_cfb64 | aes_cbc128 | aes_cfb8 | aes_cfb128| aes_cbc256 | aes_ige256 | aes_gcm | chacha20_poly1305 | 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.

block_encrypt(Type, Key, PlainText) -> CipherText Encrypt PlainText according to Type block cipher 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 Decrypt CipherText according to Type block cipher 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} Encrypt PlainText according to Type block cipher Type = block_cipher() AeadType = aead_cipher() Key = block_key() PlainText = iodata() AAD = IVec = CipherText = CipherTag = binary()

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 Decrypt CipherText according to Type block cipher 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 Convert binary representation, of an integer, to an Erlang 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 Computes the shared secret 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 XOR data 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} Generates a public keys of type Type 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() | ecdh_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

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}] Provides information about the libraries used by crypto. 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">>}]

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 Computes the function: N^P mod M 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 Decrypts CipherText using the private Key. 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 Encrypts PlainText using the private Key. 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 Decrypts CipherText using the public Key. 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 Encrypts PlainText using the public Key. 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_bytes(N) -> binary() Generate a binary of random bytes N = integer()

Generates N bytes randomly uniform 0..255, and returns the result in a binary. Uses the crypto library pseudo-random number generator.

This function is not recommended for cryptographic purposes. Please use strong_rand_bytes/1 instead.

 rand_seed(Seed) -> ok Set the seed for random bytes generation 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 returns low_entropy

 rand_uniform(Lo, Hi) -> N Generate a random number Lo, Hi, N = integer()

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

 sign(Algorithm, DigestType, Msg, Key) -> binary() Create digital signature. 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).

Equivalent to application:start(crypto).

 stop() -> ok Equivalent to application:stop(crypto).

Equivalent to application:stop(crypto).

 strong_rand_bytes(N) -> binary() Generate a binary of random bytes 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 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} 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 Provide a list of available crypto algorithms. 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 Provide a list of available named elliptic curves. EllipticCurveList = [ec_named_curve()]

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

 ec_curve(NamedCurve) -> EllipticCurve Get the defining parameters of a elliptic curve. NamedCurve = ec_named_curve() EllipticCurve = ec_explicit_curve()

Return the defining parameters of a elliptic curve.

 verify(Algorithm, DigestType, Msg, Signature, Key) -> boolean() Verifies a digital signature. 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