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crypto Crypto Functions

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]

The actual supported algorithms and features depends on their availability in the actual libcrypto used. See the 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.

Ciphers

Stream ciphers for stream_encrypt/2 and stream_decrypt/2 .

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

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

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

Digests

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

 Elliptic Curves

Note that some curves are disabled if FIPS is enabled.

Parametric curve definition.

Curve definition details.

 Keys

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

A key for des3 is a list of three iolists

Always binary() when used as return value

 Public/Private Keys 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() = [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.

 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_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

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

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

The RSA options are experimental.

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

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

 Public Key Sign and Verify

Algorithms for sign and verify.

Options for sign and verify.

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_params() = [P, G] | [P, G, PrivateKeyBitLength] Types for Engines

The result of a call to engine_load/3.

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.

The password of the key stored in an engine.

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

Internal data types

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

Encrypt PlainText according to Type block cipher

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.

Decrypt CipherText according to Type block cipher

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} Encrypt PlainText according to Type block cipher Type = 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 PlainTextaccording 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 Decrypt CipherText according to Type block cipher Type = 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 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 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.

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

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

Computes the shared secret

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

XOR data

Performs bit-wise XOR (exclusive or) on the data supplied.

 Generates a public key of type Type

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.

RSA key generation is only available if the runtime was built with dirty scheduler support. Otherwise, attempting to generate an RSA key will raise exception error:notsup.

Computes a message digest of type Type from Data.

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

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

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.

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.

Computes a HMAC of type Type from Data using Key as the authentication key.

MacLength will limit the size of the resultant Mac.

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.

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 libcrypto API.

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.

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.

 Calculates the Cipher-based Message Authentication Code.

Computes a CMAC of type Type from Data using Key as the authentication key.

MacLength will limit the size of the resultant Mac.

 Provides information about the FIPS operating status.

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.

In FIPS mode all non-FIPS compliant algorithms are disabled and raise exception error:notsup. Check supports that in FIPS mode returns the restricted list of available algorithms.

 Change FIPS mode.

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.

Provides information about the libraries used by crypto.

Provides the name and version of the libraries used by crypto.

Name is the name of the library. VerNum is the numeric version according to the library's own versioning scheme. VerStr contains a text variant of the version.

> info_lib().
[{<<"OpenSSL">>,269484095,<<"OpenSSL 1.1.0c  10 Nov 2016"">>}]

From OTP R16 the numeric version represents the version of the OpenSSL header files (openssl/opensslv.h) used when crypto was compiled. The text variant represents the libcrypto library used at runtime. In earlier OTP versions both numeric and text was taken from the library.

Computes the function: N^P mod M

Computes the function N^P mod M.

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.

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

 Decrypts CipherText using the private Key.

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]

Encrypts PlainText using the private 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]

Decrypts CipherText using the public Key.

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]

Encrypts PlainText using the public 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]

Set the seed for random bytes generation

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 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.

 Equivalent to application:start(crypto).

Equivalent to application:start(crypto).

 Equivalent to application:stop(crypto).

Equivalent to application:stop(crypto).

 Generate a binary of random bytes

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".

 Strong random number generation plugin 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[
 Strong random number generation plugin 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".

The state returned from this function cannot be used to get a reproducable random sequence as from the other rand functions, since reproducability does not match cryptographically safe.

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

rand_seed_alg(Alg) -> rand:state() Strong random number generation plugin state Alg = crypto | crypto_cache

Creates state object for random number generation, in order to generate cryptographically strong random numbers, and saves it in the process dictionary before returning it as well. 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".

Example

_ = crypto:rand_seed_alg(crypto_cache),
_IntegerValue = rand:uniform(42), % [1; 42]
_FloatValue = rand:uniform().     % [0.0; 1.0[
 rand_seed_alg(Alg, Seed) -> rand:state() Strong random number generation plugin state Alg = crypto_aes

Creates a state object for random number generation, in order to generate cryptographically unpredictable random numbers, and saves it in the process dictionary before returning it as well. See also rand_seed_alg_s/2.

Example

_ = crypto:rand_seed_alg(crypto_aes, "my seed"),
IntegerValue = rand:uniform(42), % [1; 42]
FloatValue = rand:uniform(),     % [0.0; 1.0[
_ = crypto:rand_seed_alg(crypto_aes, "my seed"),
IntegerValue = rand:uniform(42), % Same values
FloatValue = rand:uniform().     % again
rand_seed_alg_s(Alg) -> rand:state() Strong random number generation plugin state Alg = crypto | crypto_cache

Creates state object for random number generation, in order to generate cryptographically strongly random numbers. See also rand:seed_s/1.

If Alg is crypto this function behaves exactly like rand_seed_s/0.

If Alg is crypto_cache this function fetches random data with OpenSSL's RAND_bytes and caches it for speed using an internal word size of 56 bits that makes calculations fast on 64 bit machines.

When using the state object from this function the rand functions using it may 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.

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

The state returned from this function cannot be used to get a reproducable random sequence as from the other rand functions, since reproducability does not match cryptographically safe.

In fact since random data is cached some numbers may get reproduced if you try, but this is unpredictable.

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

rand_seed_alg_s(Alg, Seed) -> rand:state() Strong random number generation plugin state Alg = crypto_aes

Creates a state object for random number generation, in order to generate cryptographically unpredictable random numbers. See also rand_seed_alg/1.

To get a long period the Xoroshiro928 generator from the rand module is used as a counter (with period 2^928 - 1) and the generator states are scrambled through AES to create 58-bit pseudo random values.

The result should be statistically completely unpredictable random values, since the scrambling is cryptographically strong and the period is ridiculously long. But the generated numbers are not to be regarded as cryptographically strong since there is no re-keying schedule.

If you need cryptographically strong random numbers use rand_seed_alg_s/1 with Alg =:= crypto or Alg =:= crypto_cache.

If you need to be able to repeat the sequence use this function.

If you do not need the statistical quality of this function, there are faster algorithms in the rand module.

Thanks to the used generator the state object supports the rand:jump/0,1 function with distance 2^512.

Numbers are generated in batches and cached for speed reasons. The cache size can be changed from its default value using the crypto app's configuration parameter rand_cache_size.

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

For keylengths see the User's Guide.

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.

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.

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.

 Provide a list of available crypto algorithms.

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.

Provide a list of available named elliptic curves.

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

 Get the defining parameters of a elliptic curve.

Return the defining parameters of a elliptic curve.

 Create digital signature.

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.

 Verifies a digital signature.

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.

 Fetches a public key from an Engine stored private key.

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.

Return list of all possible engine methods

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.

Dynamical load an encryption engine

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.

Dynamical load an encryption engine

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.

Dynamical load an encryption engine

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.

Get a reference to an already loaded engine

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.

Sends ctrl commands to an OpenSSL engine

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.

Sends ctrl commands to an OpenSSL engine

Sends ctrl commands to the OpenSSL engine given by Engine. Optional is a boolean argument that can relax the semantics of the function. If set to true it will only return failure if the ENGINE supported the given command name but failed while executing it, if the ENGINE doesn't support the command name it will simply return success without doing anything. In this case we assume the user is only supplying commands specific to the given ENGINE so we set this to false.

The function 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.

Add engine to OpenSSL internal list

Add the engine to OpenSSL's internal list.

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.

Remove engine to OpenSSL internal list

Remove the engine from OpenSSL's internal list.

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.

Fetch engine ID

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

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.

Fetch engine name

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

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.

List the known engine ids

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 encryption engine just loaded once

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.

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.

Ensure encryption engine just loaded once

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.

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.

Unload an engine loaded with the ensure function

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.

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.

Unload an engine loaded with the ensure function

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.

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.