## table of contents

- buster 1:21.2.6+dfsg-1
- testing 1:23.2.6+dfsg-1
- unstable 1:23.2.6+dfsg-1
- experimental 1:24.0.5+dfsg-1

crypto(3erl) | Erlang Module Definition | crypto(3erl) |

# NAME¶

crypto - Crypto Functions# DESCRIPTION¶

This module provides a set of cryptographic functions.**Hash functions:**

**SHA1, SHA2:**- Secure Hash Standard [FIPS PUB 180-4]
**SHA3:**- SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions [FIPS PUB 202]
**MD5:**- The MD5 Message Digest Algorithm [RFC 1321]
**MD4:**- The MD4 Message Digest Algorithm [RFC 1320]

**MACs - Message Authentication Codes:**

**Hmac functions:**- Keyed-Hashing for Message Authentication [RFC 2104]
**Cmac functions:**- The AES-CMAC Algorithm [RFC 4493]
**POLY1305:**- ChaCha20 and Poly1305 for IETF Protocols [RFC 7539]

**Symmetric Ciphers:**

**DES, 3DES and AES:**- Block Cipher Techniques [NIST]
**Blowfish:**- Fast Software Encryption, Cambridge Security Workshop Proceedings (December 1993), Springer-Verlag, 1994, pp. 191-204.
**Chacha20:**- ChaCha20 and Poly1305 for IETF Protocols [RFC 7539]
**Chacha20_poly1305:**- ChaCha20 and Poly1305 for IETF Protocols [RFC 7539]

**Modes:**

**ECB, CBC, CFB, OFB and CTR:**- Recommendation for Block Cipher Modes of Operation: Methods and Techniques [NIST SP 800-38A]
**GCM:**- Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC [NIST SP 800-38D]
**CCM:**- Recommendation for Block Cipher Modes of Operation: The CCM Mode for Authentication and Confidentiality [NIST SP 800-38C]

**Asymetric Ciphers - Public Key Techniques:**

**RSA:**- PKCS #1: RSA Cryptography Specifications [RFC 3447]
**DSS:**- Digital Signature Standard (DSS) [FIPS 186-4]
**ECDSA:**- Elliptic Curve Digital Signature Algorithm [ECDSA]
**SRP:**- The SRP Authentication and Key Exchange System [RFC 2945]

**Note:**

**crypto (App)**about dependencies.

Enabling FIPS mode will also disable algorithms and features.

The **CRYPTO User's Guide** has more information on FIPS,
Engines and Algorithm Details like key lengths.

# DATA TYPES¶

## Ciphers¶

stream_cipher()= rc4 | aes_ctr | chacha20

Stream ciphers for **stream_encrypt/2** and
**stream_decrypt/2** .

block_cipher_with_iv()=cbc_cipher()|cfb_cipher()| aes_cbc128 | aes_cbc256 | aes_ige256 | blowfish_ofb64 | des3_cbf | des_ede3 | rc2_cbc

cbc_cipher()= des_cbc | des3_cbc | aes_cbc | blowfish_cbc

cfb_cipher()= aes_cfb128 | aes_cfb8 | blowfish_cfb64 | des3_cfb | des_cfb

Block ciphers with initialization vector for
**block_encrypt/4** and **block_decrypt/4** .

block_cipher_without_iv()=ecb_cipher()

ecb_cipher()= des_ecb | blowfish_ecb | aes_ecb

Block ciphers without initialization vector for
**block_encrypt/3** and **block_decrypt/3** .

aead_cipher()= aes_gcm | aes_ccm | chacha20_poly1305

Ciphers with simultaneous MAC-calculation or MAC-checking.
**block_encrypt/4** and **block_decrypt/4** .

## Digests¶

sha1()= sha

sha2()= sha224 | sha256 | sha384 | sha512

sha3()= sha3_224 | sha3_256 | sha3_384 | sha3_512

compatibility_only_hash()= md5 | md4

The *compatibility_only_hash()* algorithms are recommended
only for compatibility with existing applications.

rsa_digest_type()=sha1()|sha2()| md5 | ripemd160

dss_digest_type()=sha1()|sha2()

ecdsa_digest_type()=sha1()|sha2()

## Elliptic Curves¶

ec_named_curve()= brainpoolP160r1 | brainpoolP160t1 | brainpoolP192r1 | brainpoolP192t1 | brainpoolP224r1 | brainpoolP224t1 | brainpoolP256r1 | brainpoolP256t1 | brainpoolP320r1 | brainpoolP320t1 | brainpoolP384r1 | brainpoolP384t1 | brainpoolP512r1 | brainpoolP512t1 | c2pnb163v1 | c2pnb163v2 | c2pnb163v3 | c2pnb176v1 | c2pnb208w1 | c2pnb272w1 | c2pnb304w1 | c2pnb368w1 | c2tnb191v1 | c2tnb191v2 | c2tnb191v3 | c2tnb239v1 | c2tnb239v2 | c2tnb239v3 | c2tnb359v1 | c2tnb431r1 | ipsec3 | ipsec4 | prime192v1 | prime192v2 | prime192v3 | prime239v1 | prime239v2 | prime239v3 | prime256v1 | secp112r1 | secp112r2 | secp128r1 | secp128r2 | secp160k1 | secp160r1 | secp160r2 | secp192k1 | secp192r1 | secp224k1 | secp224r1 | secp256k1 | secp256r1 | secp384r1 | secp521r1 | sect113r1 | sect113r2 | sect131r1 | sect131r2 | sect163k1 | sect163r1 | sect163r2 | sect193r1 | sect193r2 | sect233k1 | sect233r1 | sect239k1 | sect283k1 | sect283r1 | sect409k1 | sect409r1 | sect571k1 | sect571r1 | wtls1 | wtls10 | wtls11 | wtls12 | wtls3 | wtls4 | wtls5 | wtls6 | wtls7 | wtls8 | wtls9

edwards_curve_dh()= x25519 | x448

edwards_curve_ed()= ed25519 | ed448

Note that some curves are disabled if FIPS is enabled.

ec_explicit_curve()= {Field ::ec_field(), Curve ::ec_curve(), BasePoint :: binary(), Order :: binary(), CoFactor :: none | binary()}

ec_field()=ec_prime_field()|ec_characteristic_two_field()

ec_curve()= {A :: binary(), B :: binary(), Seed :: none | binary()}

Parametric curve definition.

ec_prime_field()= {prime_field, Prime :: integer()}

ec_characteristic_two_field()= {characteristic_two_field, M :: integer(), Basis ::ec_basis()}

ec_basis()= {tpbasis, K :: integer() >= 0} | {ppbasis, K1 :: integer() >= 0, K2 :: integer() >= 0, K3 :: integer() >= 0} | onbasis

Curve definition details.

## Keys¶

key()= iodata()

des3_key()= [key()]

For keylengths, iv-sizes and blocksizes see the **User's
Guide**.

A key for des3 is a list of three iolists

key_integer()= integer() | binary()

Always *binary()* when used as return value

## Public/Private Keys¶

rsa_public()= [key_integer()]

rsa_private()= [key_integer()]

rsa_params()= {ModulusSizeInBits :: integer(), PublicExponent ::key_integer()}

rsa_public() = [E, N]

rsa_private() = [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_integer()]

dss_private()= [key_integer()]

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

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

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

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

ecdsa_public()=key_integer()

ecdsa_private()=key_integer()

ecdsa_params()=ec_named_curve()|ec_explicit_curve()

eddsa_public()=key_integer()

eddsa_private()=key_integer()

eddsa_params()=edwards_curve_ed()

srp_public()=key_integer()

srp_private()=key_integer()

srp_public() = key_integer()

Where is *A* or *B* from SRP design

srp_private() = key_integer()

Where is *a* or *b* from SRP design

srp_gen_params()= {user,srp_user_gen_params()} | {host,srp_host_gen_params()}

srp_comp_params()= {user,srp_user_comp_params()} | {host,srp_host_comp_params()}

srp_user_gen_params() = [DerivedKey::binary(), Prime::binary(), Generator::binary(), Version::atom()]

srp_host_gen_params() = [Verifier::binary(), Prime::binary(), Version::atom() ]

srp_user_comp_params() = [DerivedKey::binary(), Prime::binary(), Generator::binary(), Version::atom() | ScramblerArg::list()]

srp_host_comp_params() = [Verifier::binary(), Prime::binary(), Version::atom() | ScramblerArg::list()]

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'

## Public Key Ciphers¶

pk_encrypt_decrypt_algs()= rsa

Algorithms for public key encrypt/decrypt. Only RSA is supported.

pk_encrypt_decrypt_opts()= [rsa_opt()] |rsa_compat_opts()

rsa_opt()= {rsa_padding,rsa_padding()} | {signature_md, atom()} | {rsa_mgf1_md, sha} | {rsa_oaep_label, binary()} | {rsa_oaep_md, sha}

rsa_padding()= rsa_pkcs1_padding | rsa_pkcs1_oaep_padding | rsa_sslv23_padding | rsa_x931_padding | rsa_no_padding

Options for public key encrypt/decrypt. Only RSA is supported.

**Warning:**

The RSA options are experimental.

The exact set of options and there syntax *may* be changed
without prior notice.

rsa_compat_opts()= [{rsa_pad,rsa_padding()}] |rsa_padding()

Those option forms are kept only for compatibility and should not be used in new code.

## Public Key Sign and Verify¶

pk_sign_verify_algs()= rsa | dss | ecdsa | eddsa

Algorithms for sign and verify.

pk_sign_verify_opts()= [rsa_sign_verify_opt()]

rsa_sign_verify_opt()= {rsa_padding,rsa_sign_verify_padding()} | {rsa_pss_saltlen, integer()}

rsa_sign_verify_padding()= rsa_pkcs1_padding | rsa_pkcs1_pss_padding | rsa_x931_padding | rsa_no_padding

Options for sign and verify.

**Warning:**

The RSA options are experimental.

The exact set of options and there syntax *may* be changed
without prior notice.

## Diffie-Hellman Keys and parameters¶

dh_public()=key_integer()

dh_private()=key_integer()

dh_params()= [key_integer()]

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

ecdh_public()=key_integer()

ecdh_private()=key_integer()

ecdh_params()=ec_named_curve()|edwards_curve_dh()|ec_explicit_curve()

## Types for Engines¶

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

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 password of the key stored in an engine.

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 | engine_method_ec

engine_cmnd()= {unicode:chardata(),unicode:chardata()}

Pre and Post commands for **engine_load/3 and /4**.

## Internal data types¶

stream_state()

hmac_state()

hash_state()

Contexts with an internal state that should not be manipulated but passed between function calls.

# EXPORTS¶

block_encrypt(Type :: block_cipher_without_iv(),Key :: key(),PlainText :: iodata()) ->binary()

Encrypt *PlainText* according to *Type* block
cipher.

May raise exception *error:notsup* in case the chosen
*Type* is not supported by the underlying libcrypto implementation.

For keylengths and blocksizes see the **User's Guide**.

block_decrypt(Type :: block_cipher_without_iv(),Key :: key(),Data :: iodata()) ->binary()

Decrypt *CipherText* according to *Type* block
cipher.

May raise exception *error:notsup* in case the chosen
*Type* is not supported by the underlying libcrypto implementation.

For keylengths and blocksizes see the **User's Guide**.

**block_encrypt(Type, Key, Ivec, PlainText) -> CipherText**

**block_encrypt(AeadType, Key, Ivec, {AAD, PlainText}) -> {CipherText,
CipherTag}**

**block_encrypt(aes_gcm | aes_ccm, Key, Ivec, {AAD, PlainText, TagLength})
-> {CipherText, CipherTag}**

Types:

**block_cipher_with_iv()**

AeadType =

**aead_cipher()**

Key =

**key()**|

**des3_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 *PlainText*according to *Type* block cipher and calculate
*CipherTag* that also authenticates the *AAD* (Associated
Authenticated Data).

May raise exception *error:notsup* in case the chosen
*Type* is not supported by the underlying libcrypto implementation.

For keylengths, iv-sizes and blocksizes see the **User's
Guide**.

**block_decrypt(Type, Key, Ivec, CipherText) -> PlainText**

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

Types:

**block_cipher_with_iv()**

AeadType =

**aead_cipher()**

Key =

**key()**|

**des3_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 *CipherText*according 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

*error:notsup* in case the chosen
*Type* is not supported by the underlying libcrypto implementation.

For keylengths, iv-sizes and blocksizes see the **User's
Guide**.

bytes_to_integer(Bin :: binary()) -> integer()

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

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

Types:

SharedSecret = binary()

OthersPublicKey =

**dh_public()**|

**ecdh_public()**|

**srp_public()**

MyPrivateKey =

**dh_private()**|

**ecdh_private()**| {

**srp_public()**,

**srp_private()**}

Params =

**dh_params()**|

**ecdh_params()**|

**srp_comp_params()**

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

exor(Bin1 :: iodata(), Bin2 :: iodata()) -> 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:

PublicKey =

**dh_public()**|

**ecdh_public()**|

**rsa_public()**|

**srp_public()**

PrivKeyIn = undefined |

**dh_private()**|

**ecdh_private()**|

**rsa_private()**| {

**srp_public()**,

**srp_private()**}

PrivKeyOut =

**dh_private()**|

**ecdh_private()**|

**rsa_private()**| {

**srp_public()**,

**srp_private()**}

Params =

**dh_params()**|

**ecdh_params()**|

**rsa_params()**|

**srp_comp_params()**

Generates a public key of type *Type*. See also
**public_key:generate_key/1**. May raise exception:

- *
*error:badarg*: an argument is of wrong type or has an illegal value,- *
*error:low_entropy*: the random generator failed due to lack of secure "randomness",- *
*error:computation_failed*: the computation fails of another reason than*low_entropy*.

**Note:**

*error:notsup*.

hash(Type, Data) -> Digest

Types:

**sha1()**|

**sha2()**|

**sha3()**| ripemd160 |

**compatibility_only_hash()**

Data = iodata()

Digest = binary()

Computes a message digest of type *Type* from
*Data*.

*error:notsup* in case the chosen
*Type* is not supported by the underlying libcrypto implementation.

hash_init(Type) -> State

Types:

**sha1()**|

**sha2()**|

**sha3()**| ripemd160 |

**compatibility_only_hash()**

State =

**hash_state()**

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

*error:notsup* in case the chosen
*Type* is not supported by the underlying libcrypto implementation.

hash_update(State, Data) -> NewState

Types:

**hash_state()**

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(State) -> Digest

Types:

**hash_state()**

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:

**sha1()**|

**sha2()**|

**sha3()**|

**compatibility_only_hash()**

Key = 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) -> State

Types:

**sha1()**|

**sha2()**|

**sha3()**|

**compatibility_only_hash()**

Key = iodata()

State =

**hmac_state()**

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(State, Data) -> NewState

Types:

State = NewState =

**hmac_state()**

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:**

*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 libcrypto API.

hmac_final(State) -> Mac

Types:

**hmac_state()**

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(State, HashLen) -> Mac

Types:

**hmac_state()**

HashLen = integer()

Mac = binary()

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:

**cbc_cipher()**|

**cfb_cipher()**| blowfish_cbc | des_ede3 | rc2_cbc

Key = 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() -> not_supported | not_enabled | enabled

Provides information about the FIPS operating status of crypto and
the underlying libcrypto 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*.

See **enable_fips_mode/1** about how to enable FIPS mode.

**Warning:**

*error:notsup*. Check

**supports**that in FIPS mode returns the restricted list of available algorithms.

enable_fips_mode(Enable) -> Result

Types:

Enables (*Enable = true*) or disables (*Enable = false*)
FIPS mode. Returns *true* if the operation was successful or
*false* otherwise.

Note that to enable FIPS mode succesfully, OTP must be built with
the configure option *--enable-fips*, and the underlying libcrypto must
also support FIPS.

See also **info_fips/0**.

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

Types:

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:**

*numeric version*represents the version of the OpenSSL

*header files*(

*openssl/opensslv.h*) used when crypto was compiled. The text variant represents the libcrypto library used at runtime. In earlier OTP versions both numeric and text was taken from the library.

mod_pow(N, P, M) -> Result

Types:

Result = binary() | error

Computes the function *N^P mod M*.

next_iv(Type :: cbc_cipher(), Data) -> NextIVec

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

Types:

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.

poly1305(Key :: iodata(), Data :: iodata()) -> Mac

Types:

Computes a POLY1305 message authentication code (*Mac*) from
*Data* using *Key* as the authentication key.

private_decrypt(Algorithm, CipherText, PrivateKey, Options) ->PlainText

Types:

**pk_encrypt_decrypt_algs()**

CipherText = binary()

PrivateKey =

**rsa_private()**|

**engine_key_ref()**

Options =

**pk_encrypt_decrypt_opts()**

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(Algorithm, PlainText, PrivateKey, Options) ->CipherText

Types:

**pk_encrypt_decrypt_algs()**

PlainText = binary()

PrivateKey =

**rsa_private()**|

**engine_key_ref()**

Options =

**pk_encrypt_decrypt_opts()**

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(Algorithm, CipherText, PublicKey, Options) ->PlainText

Types:

**pk_encrypt_decrypt_algs()**

CipherText = binary()

PublicKey =

**rsa_public()**|

**engine_key_ref()**

Options =

**pk_encrypt_decrypt_opts()**

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(Algorithm, PlainText, PublicKey, Options) ->CipherText

Types:

**pk_encrypt_decrypt_algs()**

PlainText = binary()

PublicKey =

**rsa_public()**|

**engine_key_ref()**

Options =

**pk_encrypt_decrypt_opts()**

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 :: binary()) -> ok

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** raises *error:low_entropy*

**rand_uniform(Lo, Hi) -> N**

Types:

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

start() -> ok | {error, Reason :: term()}

Equivalent to application:start(crypto).

stop() -> ok | {error, Reason :: term()}

Equivalent to application:stop(crypto).

strong_rand_bytes(N :: integer() >= 0) -> binary()

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 raise exception *error: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 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 raise exception *error: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[

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**.

When using the state object from this function the **rand**
functions using it may raise exception *error:low_entropy* in case the
random generator failed due to lack of secure "randomness".

**Note:**

**rand**functions, since reproducability does not match cryptographically safe.

The only supported usage is to generate one distinct random sequence from this start state.

**rand_seed_alg(Alg) -> rand: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 raise exception *error: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[

**rand_seed_alg_s(Alg) -> rand:state()**

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.

**rand**
functions using it may raise exception *error: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*.

**Note:**

**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.

stream_init(Type, Key) -> State

Types:

Key = iodata()

State =

**stream_state()**

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

For keylengths see the **User's Guide**.

stream_init(Type, Key, IVec) -> State

Types:

Key = iodata()

IVec = binary()

State =

**stream_state()**

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**.

For keylengths and iv-sizes see the **User's Guide**.

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

Types:

**stream_state()**

PlainText = iodata()

NewState =

**stream_state()**

CipherText = iodata()

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:

**stream_state()**

CipherText = iodata()

NewState =

**stream_state()**

PlainText = iodata()

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() -> [Support]

Types:

Hashs = [

**sha1()**|

**sha2()**|

**sha3()**| ripemd160 |

**compatibility_only_hash()**]

Ciphers = [

**stream_cipher()**|

**block_cipher_with_iv()**|

**block_cipher_without_iv()**|

**aead_cipher()**]

PKs = [rsa | dss | ecdsa | dh | ecdh | ec_gf2m]

Macs = [hmac | cmac | poly1305]

Curves = [

**ec_named_curve()**|

**edwards_curve_dh()**|

**edwards_curve_ed()**]

RSAopts = [

**rsa_sign_verify_opt()**|

**rsa_opt()**]

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

Note: the *rsa_opts* entry is in an experimental state and
may change or be removed without notice. No guarantee for the accuarcy of
the rsa option's value list should be assumed.

ec_curves() -> [EllipticCurve]

Types:

**ec_named_curve()**|

**edwards_curve_dh()**|

**edwards_curve_ed()**

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

ec_curve(CurveName) -> ExplicitCurve

Types:

**ec_named_curve()**

ExplicitCurve =

**ec_explicit_curve()**

Return the defining parameters of a elliptic curve.

sign(Algorithm, DigestType, Msg, Key) -> Signature

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

Types:

**pk_sign_verify_algs()**

DigestType =

**rsa_digest_type()**|

**dss_digest_type()**|

**ecdsa_digest_type()**| none

Msg = binary() | {digest, binary()}

Key =

**rsa_private()**|

**dss_private()**| [

**ecdsa_private()**|

**ecdsa_params()**] | [

**eddsa_private()**|

**eddsa_params()**] |

**engine_key_ref()**

Options =

**pk_sign_verify_opts()**

Signature = binary()

Creates a digital signature.

The msg is either the binary "cleartext" data to be signed or it is the hashed value of "cleartext" i.e. the digest (plaintext).

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

See also **public_key:sign/3**.

verify(Algorithm, DigestType, Msg, Signature, Key) -> Result

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

Types:

**pk_sign_verify_algs()**

DigestType =

**rsa_digest_type()**|

**dss_digest_type()**|

**ecdsa_digest_type()**

Msg = binary() | {digest, binary()}

Signature = binary()

Key =

**rsa_public()**|

**dss_public()**| [

**ecdsa_public()**|

**ecdsa_params()**] | [

**eddsa_public()**|

**eddsa_params()**] |

**engine_key_ref()**

Options =

**pk_sign_verify_opts()**

Result = boolean()

Verifies a digital signature

The msg is either the binary "cleartext" data to be signed or it is the hashed value of "cleartext" i.e. the digest (plaintext).

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

See also **public_key:verify/4**.

privkey_to_pubkey(Type, EnginePrivateKeyRef) -> PublicKey

Types:

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.

engine_get_all_methods() -> Result

Types:

**engine_method_type()**]

Returns a list of all possible engine methods.

May raise exception *error: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:

**unicode:chardata()**

PreCmds = PostCmds = [

**engine_cmnd()**]

Result = {ok, Engine ::

**engine_ref()**} | {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 raises a *error:badarg* if the parameters are in
wrong format. It may also raise the exception *error: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:

**unicode:chardata()**

PreCmds = PostCmds = [

**engine_cmnd()**]

EngineMethods = [

**engine_method_type()**]

Result = {ok, Engine ::

**engine_ref()**} | {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 raises a *error:badarg* if the parameters are in
wrong format. It may also raise the exception *error: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_ref()**

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

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

The function raises a *error:badarg* if the parameter is in
wrong format. It may also raise the exception *error: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_by_id(EngineId) -> Result

Types:

**unicode:chardata()**

Result = {ok, Engine ::

**engine_ref()**} | {error, Reason :: term()}

Get a reference to an already loaded engine with *EngineId*.
An error tuple is returned if the engine can't be unloaded.

The function raises a *error:badarg* if the parameter is in
wrong format. It may also raise the exception *error: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:

CmdName = 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 raises a *error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

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

Types:

CmdName = 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*.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

engine_add(Engine) -> Result

Types:

**engine_ref()**

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

Add the engine to OpenSSL's internal list.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

engine_remove(Engine) -> Result

Types:

**engine_ref()**

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

Remove the engine from OpenSSL's internal list.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

engine_get_id(Engine) -> EngineId

Types:

**engine_ref()**

EngineId =

**unicode:chardata()**

Return the ID for the engine, or an empty binary if there is no id set.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

engine_get_name(Engine) -> EngineName

Types:

**engine_ref()**

EngineName =

**unicode:chardata()**

Return the name (eg a description) for the engine, or an empty binary if there is no name set.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

engine_list() -> Result

Types:

**unicode:chardata()**]

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

It may also raise the exception *error:notsup* in case there
is no engine support in the underlying OpenSSL implementation.

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

May raise exception *error:notsup* in case engine
functionality is not supported by the underlying OpenSSL implementation.

ensure_engine_loaded(EngineId, LibPath) -> Result

Types:

**unicode:chardata()**

Result = {ok, Engine ::

**engine_ref()**} | {error, Reason :: term()}

Loads the OpenSSL engine given by *EngineId* and the path to
the dynamic library implementing the engine. This function is the same as
calling *ensure_engine_loaded/3* with *EngineMethods* set to a
list of all the possible methods. An error tuple is returned if the engine
can't be loaded.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

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

ensure_engine_loaded(EngineId, LibPath, EngineMethods) -> Result

Types:

**unicode:chardata()**

EngineMethods = [

**engine_method_type()**]

Result = {ok, Engine ::

**engine_ref()**} | {error, Reason :: term()}

Loads the OpenSSL engine given by *EngineId* and the path to
the dynamic library implementing the engine. This function differs from the
normal engine_load in that sense it also add the engine id to the internal
list in OpenSSL. Then in the following calls to the function it just fetch
the reference to the engine instead of loading it again. An error tuple is
returned if the engine can't be loaded.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

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

ensure_engine_unloaded(Engine) -> Result

Types:

**engine_ref()**

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

Unloads an engine loaded with the *ensure_engine_loaded*
function. It both removes the label from the OpenSSL internal engine list
and unloads the engine. This function is the same as calling
*ensure_engine_unloaded/2* with *EngineMethods* set to a list of
all the possible methods. An error tuple is returned if the engine can't be
unloaded.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

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

ensure_engine_unloaded(Engine, EngineMethods) -> Result

Types:

**engine_ref()**

EngineMethods = [

**engine_method_type()**]

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

Unloads an engine loaded with the *ensure_engine_loaded*
function. It both removes the label from the OpenSSL internal engine list
and unloads the engine. An error tuple is returned if the engine can't be
unloaded.

*error:badarg* if the parameters are in
wrong format. It may also raise the exception *error:notsup* in case
there is no engine support in the underlying OpenSSL implementation.

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

crypto 4.4 | Ericsson AB |