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.
5.1 Ciphers
A cipher in the new api is categorized as either cipher_no_iv(), cipher_iv() or cipher_aead(). The letters IV are short for Initialization Vector and AEAD is an abreviation of Authenticated Encryption with Associated Data.
Due to irregular naming conventions, some cipher names in the old api are substitued by new names in the new api. For a list of retired names, see Retired cipher names.
To dynamically check availability, check that the name in the Cipher and Mode column is present in the list returned by crypto:supports(ciphers).
Ciphers without an IV - cipher_no_iv()
To be used with:
The ciphers are:
| Cipher and Mode |
Key length [bytes] |
Block size [bytes] |
| aes_128_ecb | 16 | 16 |
| aes_192_ecb | 24 | 16 |
| aes_256_ecb | 32 | 16 |
| blowfish_ecb | 16 | 8 |
| des_ecb | 8 | 8 |
| rc4 | 16 | 1 |
Table 5.1: Ciphers without IV
Ciphers with an IV - cipher_iv()
To be used with:
The ciphers are:
| Cipher and Mode |
Key length [bytes] |
IV length [bytes] |
Block size [bytes] |
Limited to OpenSSL versions |
| aes_128_cbc | 16 | 16 | 16 | |
| aes_192_cbc | 24 | 16 | 16 | |
| aes_256_cbc | 32 | 16 | 16 | |
| aes_128_cfb8 | 16 | 16 | 1 | |
| aes_192_cfb8 | 24 | 16 | 1 | |
| aes_256_cfb8 | 32 | 16 | 1 | |
| aes_128_cfb128 | 16 | 16 | 1 | |
| aes_192_cfb128 | 24 | 16 | 1 | |
| aes_256_cfb128 | 32 | 16 | 1 | |
| aes_128_ctr | 16 | 16 | 1 | |
| aes_192_ctr | 24 | 16 | 1 | |
| aes_256_ctr | 32 | 16 | 1 | |
| blowfish_cbc | 16 | 8 | 8 | |
| blowfish_cfb64 | 16 | 8 | 1 | |
| blowfish_ofb64 | 16 | 8 | 1 | |
| chacha20 | 32 | 16 | 1 | ≥1.1.0d |
| des_cbc | 8 | 8 | 8 | |
| des_ede3_cbc | 24 | 8 | 8 | |
| des_cfb | 8 | 8 | 1 | |
| des_ede3_cfb | 24 | 8 | 1 | |
| rc2_cbc | 16 | 8 | 8 |
Table 5.2: Ciphers with IV
Ciphers with AEAD - cipher_aead()
To be used with:
The ciphers are:
| Cipher and Mode |
Key length [bytes] |
IV length [bytes] |
AAD length [bytes] |
Tag length [bytes] |
Block size [bytes] |
Limited to OpenSSL versions |
| aes_128_ccm | 16 | 7-13 | any | even 4-16 default: 12 | any | ≥1.0.1 |
| aes_192_ccm | 24 | 7-13 | any | even 4-16 default: 12 | any | ≥1.0.1 |
| aes_256_ccm | 32 | 7-13 | any | even 4-16 default: 12 | any | ≥1.0.1 |
| aes_128_gcm | 16 | ≥1 | any | 1-16 default: 16 | any | ≥1.0.1 |
| aes_192_gcm | 24 | ≥1 | any | 1-16 default: 16 | any | ≥1.0.1 |
| aes_256_gcm | 32 | ≥1 | any | 1-16 default: 16 | any | ≥1.0.1 |
| chacha20_poly1305 | 32 | 1-16 | any | 16 | any | ≥1.1.0 |
Table 5.3: AEAD ciphers
5.2 Message Authentication Codes (MACs)
To be used in mac/4 and related functions.
CMAC
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 returned by crypto:supports(macs). Also check that the name in the Cipher and Mode column is present in the list returned by crypto:supports(ciphers).
| Cipher and Mode |
Key length [bytes] |
Max Mac Length (= default length) [bytes] |
| aes_128_cbc | 16 | 16 |
| aes_192_cbc | 24 | 16 |
| aes_256_cbc | 32 | 16 |
| aes_128_ecb | 16 | 16 |
| aes_192_ecb | 24 | 16 |
| aes_256_ecb | 32 | 16 |
| blowfish_cbc | 16 | 8 |
| blowfish_ecb | 16 | 8 |
| des_cbc | 8 | 8 |
| des_ecb | 8 | 8 |
| des_ede3_cbc | 24 | 8 |
| rc2_cbc | 16 | 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 returned by crypto:supports(macs) and that the hash name is present in the list returned by crypto:supports(hashs).
| Hash |
Max Mac Length (= default length) [bytes] |
| sha | 20 |
| sha224 | 28 |
| sha256 | 32 |
| sha384 | 48 |
| sha512 | 64 |
| sha3_224 | 28 |
| sha3_256 | 32 |
| sha3_384 | 48 |
| sha3_512 | 64 |
| blake2b | 64 |
| blake2s | 32 |
| md4 | 16 |
| md5 | 16 |
| ripemd160 | 20 |
Table 5.5: HMAC output sizes
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 returned by crypto:supports(macs).
The poly1305 mac wants an 32 bytes key and produces a 16 byte MAC by default.
5.3 Hash
To dynamically check availability, check that the wanted name in the Names column is present in the list returned by crypto:supports(hashs).
| Type | Names |
Limitated to OpenSSL versions |
| SHA1 | sha | |
| SHA2 | sha224, sha256, sha384, sha512 | |
| SHA3 | sha3_224, sha3_256, sha3_384, sha3_512 | ≥1.1.1 |
| MD4 | md4 | |
| MD5 | md5 | |
| RIPEMD | ripemd160 |
Table 5.6:
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 returned by crypto:supports(public_keys).
The RSA options are experimental.
The exact set of options and there syntax may be changed without prior notice.
| Option | sign/verify |
public encrypt private decrypt |
private encrypt public decrypt |
| {rsa_padding,rsa_x931_padding} | x | x | |
| {rsa_padding,rsa_pkcs1_padding} | x | x | x |
| {rsa_padding,rsa_pkcs1_pss_padding} {rsa_pss_saltlen, -2..} {rsa_mgf1_md, atom()} |
x (2) x (2) x (2) |
||
| {rsa_padding,rsa_pkcs1_oaep_padding} {rsa_mgf1_md, atom()} {rsa_oaep_label, binary()}} {rsa_oaep_md, atom()} |
x (2) x (2) x (3) x (3) |
||
| {rsa_padding,rsa_no_padding} | x (1) |
Table 5.7:
Notes:
- (1) OpenSSL ≤ 1.0.0
- (2) OpenSSL ≥ 1.0.1
- (3) OpenSSL ≥ 1.1.0
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 returned by crypto:supports(public_keys).
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 returned by crypto:supports(public_keys). If the atom ec_gf2m also is present, the characteristic two field curves are available.
The actual supported named curves could be checked by examining the list returned by crypto:supports(curves).
EdDSA
EdDSA is available with OpenSSL 1.1.1 or later if not disabled by configuration. To dynamically check availability, check that the atom eddsa is present in the list returned by crypto:supports(public_keys).
Support for the curves ed25519 and ed448 is implemented. The actual supported named curves could be checked by examining the list with the list returned by crypto:supports(curves).
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 returned by crypto:supports(public_keys).
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 returned by crypto:supports(public_keys).
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 returned by crypto:supports(curves).