Ciphersuite

Ciphersuite types and cryptographic configuration for OpenMLS

Overview

Ciphersuites define the cryptographic algorithms used in MLS protocol operations. Each ciphersuite specifies a combination of:

• HPKE KEM (Key Encapsulation Mechanism)
• AEAD (Authenticated Encryption with Associated Data)
• Hash algorithm
• Signature scheme

Supported Ciphersuites

OpenMLS supports the following ciphersuites:

• MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519 (MTI - Mandatory to Implement)
• MLS_128_DHKEMP256_AES128GCM_SHA256_P256
• MLS_128_DHKEMX25519_CHACHA20POLY1305_SHA256_Ed25519

Ciphersuite

The main ciphersuite enum defining all supported cryptographic configurations.

Ciphersuite · enum

MLS ciphersuite enumeration

Show Variants

MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519 · 0x0001

DH KEM x25519 | AES-GCM 128 | SHA2-256 | Ed25519 (Mandatory to Implement)

MLS_128_DHKEMP256_AES128GCM_SHA256_P256 · 0x0002

DH KEM P256 | AES-GCM 128 | SHA2-256 | EcDSA P256

MLS_128_DHKEMX25519_CHACHA20POLY1305_SHA256_Ed25519 · 0x0003

DH KEM x25519 | Chacha20Poly1305 | SHA2-256 | Ed25519

MLS_256_DHKEMX448_AES256GCM_SHA512_Ed448 · 0x0004

DH KEM x448 | AES-GCM 256 | SHA2-512 | Ed448

MLS_256_DHKEMP521_AES256GCM_SHA512_P521 · 0x0005

DH KEM P521 | AES-GCM 256 | SHA2-512 | EcDSA P521

MLS_256_DHKEMX448_CHACHA20POLY1305_SHA512_Ed448 · 0x0006

DH KEM x448 | Chacha20Poly1305 | SHA2-512 | Ed448

MLS_256_DHKEMP384_AES256GCM_SHA384_P384 · 0x0007

DH KEM P384 | AES-GCM 256 | SHA2-384 | EcDSA P384

MLS_256_XWING_CHACHA20POLY1305_SHA256_Ed25519 · 0x004D

X-WING KEM draft-01 | Chacha20Poly1305 | SHA2-256 | Ed25519

Methods

Algorithm Accessors

hash_algorithm · fn(&self) -> HashType

Returns the hash algorithm for this ciphersuite

pub const fn hash_algorithm(&self) -> HashType

signature_algorithm · fn(&self) -> SignatureScheme

Returns the signature scheme for this ciphersuite

pub const fn signature_algorithm(&self) -> SignatureScheme

aead_algorithm · fn(&self) -> AeadType

Returns the AEAD algorithm for this ciphersuite

pub const fn aead_algorithm(&self) -> AeadType

hpke_kdf_algorithm · fn(&self) -> HpkeKdfType

Returns the HPKE KDF algorithm for this ciphersuite

pub const fn hpke_kdf_algorithm(&self) -> HpkeKdfType

hpke_kem_algorithm · fn(&self) -> HpkeKemType

Returns the HPKE KEM algorithm for this ciphersuite

pub const fn hpke_kem_algorithm(&self) -> HpkeKemType

hpke_aead_algorithm · fn(&self) -> HpkeAeadType

Returns the HPKE AEAD algorithm for this ciphersuite

pub const fn hpke_aead_algorithm(&self) -> HpkeAeadType

hpke_config · fn(&self) -> HpkeConfig

Returns the complete HPKE configuration (KEM, KDF, AEAD) for this ciphersuite

pub const fn hpke_config(&self) -> HpkeConfig

Length Accessors

hash_length · fn(&self) -> usize

Returns the output length of the hash algorithm in bytes

pub const fn hash_length(&self) -> usize

mac_length · fn(&self) -> usize

Returns the length of the AEAD tag in bytes

pub const fn mac_length(&self) -> usize

aead_key_length · fn(&self) -> usize

Returns the key size of the AEAD in bytes

pub const fn aead_key_length(&self) -> usize

aead_nonce_length · fn(&self) -> usize

Returns the nonce length of the AEAD in bytes

pub const fn aead_nonce_length(&self) -> usize

Supporting Types

HashType

HashType · enum

Hash algorithm types

Show Variants

Sha2_256 · 0x04

SHA-256 (32 byte output)

Sha2_384 · 0x05

SHA-384 (48 byte output)

Sha2_512 · 0x06

SHA-512 (64 byte output)

AeadType

AeadType · enum

AEAD algorithm types

Show Variants

Aes128Gcm · 0x0001

AES-GCM 128 (16 byte key, 16 byte tag)

Aes256Gcm · 0x0002

AES-GCM 256 (32 byte key, 16 byte tag)

ChaCha20Poly1305 · 0x0003

ChaCha20-Poly1305 (32 byte key, 16 byte tag)

HpkeKemType

HpkeKemType · enum

HPKE Key Encapsulation Mechanism types

Show Variants

DhKemP256 · 0x0010

DH KEM on P-256

DhKemP384 · 0x0011

DH KEM on P-384

DhKemP521 · 0x0012

DH KEM on P-521

DhKem25519 · 0x0020

DH KEM on X25519

DhKem448 · 0x0021

DH KEM on X448

XWingKemDraft6 · 0x004D

XWing combiner for ML-KEM and X25519

HpkeKdfType

HpkeKdfType · enum

HPKE Key Derivation Function types

Show Variants

HkdfSha256 · 0x0001

HKDF-SHA-256

HkdfSha384 · 0x0002

HKDF-SHA-384

HkdfSha512 · 0x0003

HKDF-SHA-512

HpkeAeadType

HpkeAeadType · enum

HPKE AEAD types

Show Variants

AesGcm128 · 0x0001

AES-GCM 128

AesGcm256 · 0x0002

AES-GCM 256

ChaCha20Poly1305 · 0x0003

ChaCha20-Poly1305

Export · 0xFFFF

Export-only mode

Usage Example

use openmls::prelude::*;

let ciphersuite = Ciphersuite::MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519;

// Get cryptographic components
let hash_alg = ciphersuite.hash_algorithm();
let sig_scheme = ciphersuite.signature_algorithm();
let aead_alg = ciphersuite.aead_algorithm();

// Get algorithm lengths
let hash_len = ciphersuite.hash_length(); // 32 bytes for SHA-256
let mac_len = ciphersuite.mac_length();   // 16 bytes for AES-GCM

// Get HPKE configuration
let hpke_config = ciphersuite.hpke_config();