Module hpke 

Public-Key Encryption

As with signing, MLS includes a label and context in encryption operations to avoid confusion between ciphertexts produced for different purposes. Encryption and decryption including this label and context are done as follows:

EncryptWithLabel(PublicKey, Label, Context, Plaintext) =
  SealBase(PublicKey, EncryptContext, "", Plaintext)

DecryptWithLabel(PrivateKey, Label, Context, KEMOutput, Ciphertext) =
  OpenBase(KEMOutput, PrivateKey, EncryptContext, "", Ciphertext)

Where EncryptContext is specified as:

struct {
  opaque label<V>;
  opaque context<V>;
} EncryptContext;

And its fields set to:

label = "MLS 1.0 " + Label;
context = Context;

Here, the functions SealBase and OpenBase are defined RFC9180, using the HPKE algorithms specified by the group’s ciphersuite. If MLS extensions require HPKE encryption operations, they should re-use the EncryptWithLabel construction, using a distinct label. To avoid collisions in these labels, an IANA registry is defined in mls-public-key-encryption-labels.

Structs

EncryptContext

Context for HPKE encryption

Enums

Error

HPKE labeled encryption errors.

Functions

decrypt_with_label

Decrypt with HPKE and label.

encrypt_with_label

Encrypt to an HPKE key with a label.