5 Algorithm Details

This chapter describes details of algorithms in the crypto application.

The tables only documents the supported cryptos and key lengths. The user should not draw any conclusion on security from the supplied tables.

5.2 Message Authentication Codes (MACs)

CMAC

To be used in cmac/3 and cmac/4.

CMAC with the following ciphers are available with OpenSSL 1.0.1 or later if not disabled by configuration.

To dynamically check availability, check that the name cmac is present in the list with the macs tag in the return value of crypto:supports(). Also check that the name in the Cipher and Mode column is present in the list with the cipher tag in the return value.

Cipher and Mode	Key length [bytes]	Max Mac Length [bytes]
aes_cbc	16, 24, 32	16
aes_cbc128	16	16
aes_cbc256	32	16
aes_cfb8	16	1
blowfish_cbc	4-56	8
blowfish_cfb64	1-	1
blowfish_ecb	1-	8
blowfish_ofb64	1-	1
des3_cbc (=DES EDE3 CBC)	[8,8,8]	8
des3_cfb (=DES EDE3 CFB)	[8,8,8]	1
des_cbc	8	8
des_cfb	8	1
des_ecb	8	1
rc2_cbc	1-	8

Table 5.4: CMAC cipher key lengths

HMAC

Available in all OpenSSL compatible with Erlang CRYPTO if not disabled by configuration.

To dynamically check availability, check that the name hmac is present in the list with the macs tag in the return value of crypto:supports().

POLY1305

POLY1305 is available with OpenSSL 1.1.1 or later if not disabled by configuration.

To dynamically check availability, check that the name poly1305 is present in the list with the macs tag in the return value of crypto:supports().

5.3 Hash

To dynamically check availability, check that the wanted name in the Names column is present in the list with the hashs tag in the return value of crypto:supports().

Type	Names	Supported with OpenSSL versions
SHA1	sha	all
SHA2	sha224, sha256, sha384, sha512	all
SHA3	sha3_224, sha3_256, sha3_384, sha3_512	1.1.1 -
MD4	md4	all
MD5	md5	all
RIPEMD	ripemd160	all

Table 5.5:

5.4 Public Key Cryptography

RSA

RSA is available with all OpenSSL versions compatible with Erlang CRYPTO if not disabled by configuration. To dynamically check availability, check that the atom rsa is present in the list with the public_keys tag in the return value of crypto:supports().

Warning

The RSA options are experimental.

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

Option	sign/verify	encrypt/decrypt	Supported with OpenSSL versions
{rsa_mgf1_md,atom()}	x	x	1.0.1
{rsa_oaep_label, binary()}		x
{rsa_oaep_md, atom()}		x
{rsa_padding,rsa_pkcs1_pss_padding}	x		1.0.0
{rsa_pss_saltlen, -2..}	x		1.0.0
{rsa_padding,rsa_no_padding}	x	x
{rsa_padding,rsa_pkcs1_padding}	x	x
{rsa_padding,rsa_sslv23_padding}		x
{rsa_padding,rsa_x931_padding}	x

Table 5.6:

DSS

DSS is available with OpenSSL versions compatible with Erlang CRYPTO if not disabled by configuration. To dynamically check availability, check that the atom dss is present in the list with the public_keys tag in the return value of crypto:supports().

ECDSA

ECDSA is available with OpenSSL 0.9.8o or later if not disabled by configuration. To dynamically check availability, check that the atom ecdsa is present in the list with the public_keys tag in the return value of crypto:supports(). If the atom ec_gf2m characteristic two field curves are available.

The actual supported named curves could be checked by examining the list with the curves tag in the return value of crypto:supports().

Diffie-Hellman

Diffie-Hellman computations are available with OpenSSL versions compatible with Erlang CRYPTO if not disabled by configuration. To dynamically check availability, check that the atom dh is present in the list with the public_keys tag in the return value of crypto:supports().

Elliptic Curve Diffie-Hellman

Elliptic Curve Diffie-Hellman is available with OpenSSL 0.9.8o or later if not disabled by configuration. To dynamically check availability, check that the atom ecdh is present in the list with the public_keys tag in the return value of crypto:supports().

The Edward curves x25519 and x448 are supported with OpenSSL 1.1.1 or later if not disabled by configuration.

The actual supported named curves could be checked by examining the list with the curves tag in the return value of crypto:supports().

Cipher and Mode	Key length [bytes]	IV length [bytes]	AAD length [bytes]	Tag length [bytes]	Block size [bytes]	Supported with OpenSSL versions
aes_ccm	16,24,32	7-13	any	even 4-16 default: 12	any	1.1.0 -
aes_gcm	16,24,32	1-	any	1-16 default: 16	any	1.1.0 -
chacha20_poly1305	32	1-16	any	16	any	1.1.0 -

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