# `Cmsex.RecipientInfo`
[🔗](https://github.com/openspb/cmsex/blob/v0.1.0/lib/cmsex/recipient_info.ex#L1)

One recipient of an EnvelopedData, AuthEnvelopedData or AuthenticatedData
message, as `Cmsex.decode/2` reads it (RFC 5652, 6.2): the means by which
that recipient gets the content-encryption key.

Fields:

  * `:type` - which kind of RecipientInfo:
    * `:key_transport` - the key encrypted to the public key of a
      certificate, with RSA (KeyTransRecipientInfo);
    * `:key_agreement` - a key wrapped with one agreed with ECDH or X25519
      and X448 (KeyAgreeRecipientInfo), for one or more recipients;
    * `:kek` - the key wrapped with a symmetric key the parties share
      (KEKRecipientInfo);
    * `:password` - the key wrapped with one derived from a password
      (PasswordRecipientInfo);
    * `:other` - an OtherRecipientInfo, which this library does not
      decrypt.
  * `:version` - the version written in the message; `nil` for `:other`.
  * `:rid` - which key the recipient holds: for `:key_transport`,
    `{:issuer_and_serial, issuer, serial}`, with the issuer as the DER of
    its Name as received, or `{:subject_key_identifier, ski}`; for `:kek`,
    `{:kek, key_identifier}`; `nil` for the others.
  * `:key_encryption_algorithm` - the name of the key-encryption
    algorithm in `Cmsex.OID`, or its OID: `:rsaes_oaep` or
    `:rsa_encryption`; a key agreement scheme, such as
    `:std_dh_sha256kdf`; a key wrap, such as `:aes256_wrap`; or
    `:pwri_kek`.
  * `:encrypted_key` - the encrypted key; `nil` for `:key_agreement`,
    which has one per recipient, and for `:other`.
  * `:originator` - for `:key_agreement`, the key of the sender:
    `{:public_key, algorithm, key}`, with the algorithm as a name such as
    `:ec_public_key` or `:x25519` and the key as the bytes of the public
    key (an EC point, or the raw X25519 or X448 key), or a certificate,
    as `{:issuer_and_serial, issuer, serial}` or
    `{:subject_key_identifier, ski}`.
  * `:ukm` - for `:key_agreement`, the user keying material, or `nil`.
  * `:key_wrap_algorithm` - for `:key_agreement`, the key wrap the
    scheme uses, such as `:aes128_wrap`, or `nil` when the parameters do
    not name one.
  * `:recipient_encrypted_keys` - for `:key_agreement`, a list of
    `{rid, encrypted_key}`, with `rid` as `:rid` above. The date and the
    other attribute of a RecipientKeyIdentifier are not read.
  * `:date` - for `:kek`, the date of the KEKIdentifier, or `nil`.
  * `:key_derivation_algorithm` - for `:password`, the name of the key
    derivation algorithm, such as `:pbkdf2`, or `nil` when absent.
  * `:other_type` - for `:other`, the oriType.
  * `:deviations` - what the library tolerated when reading, against
    RFC 5652: `:recipient_info_version` when the version is not the one
    the type and the identifier call for.

# `originator`

```elixir
@type originator() ::
  {:public_key, atom() | tuple(), binary()}
  | {:issuer_and_serial, binary(), integer()}
  | {:subject_key_identifier, binary()}
```

# `rid`

```elixir
@type rid() ::
  {:issuer_and_serial, binary(), integer()}
  | {:subject_key_identifier, binary()}
  | {:kek, binary()}
```

# `t`

```elixir
@type t() :: %Cmsex.RecipientInfo{
  date: DateTime.t() | nil,
  deviations: [atom()],
  encrypted_key: binary() | nil,
  key_derivation_algorithm: atom() | tuple() | nil,
  key_encryption_algorithm: atom() | tuple() | nil,
  key_wrap_algorithm: atom() | tuple() | nil,
  originator: originator() | nil,
  other_type: atom() | tuple() | nil,
  raw: map() | nil,
  recipient_encrypted_keys: [{rid(), binary()}],
  rid: rid() | nil,
  type: :key_transport | :key_agreement | :kek | :password | :other,
  ukm: binary() | nil,
  version: non_neg_integer() | nil
}
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*