Class SKESessionKeyV4

pgpy/packet/packets.py:496–610

5.3. Symmetric-Key Encrypted Session Key Packets (Tag 3) The Symmetric-Key Encrypted Session Key packet holds the symmetric-key encryption of a session key used to encrypt a message. Zero or more Public-Key Encrypted Session Key packets and/or Symmetric-Key Encrypted Session K

class SKESessionKeyV4(SKESessionKey):
    """
    5.3.  Symmetric-Key Encrypted Session Key Packets (Tag 3)

    The Symmetric-Key Encrypted Session Key packet holds the
    symmetric-key encryption of a session key used to encrypt a message.
    Zero or more Public-Key Encrypted Session Key packets and/or
    Symmetric-Key Encrypted Session Key packets may precede a
    Symmetrically Encrypted Data packet that holds an encrypted message.
    The message is encrypted with a session key, and the session key is
    itself encrypted and stored in the Encrypted Session Key packet or
    the Symmetric-Key Encrypted Session Key packet.

    If the Symmetrically Encrypted Data packet is preceded by one or
    more Symmetric-Key Encrypted Session Key packets, each specifies a
    passphrase that may be used to decrypt the message.  This allows a
    message to be encrypted to a number of public keys, and also to one
    or more passphrases.  This packet type is new and is not generated
    by PGP 2.x or PGP 5.0.

    The body of this packet consists of:

     - A one-octet version number.  The only currently defined version
       is 4.

     - A one-octet number describing the symmetric algorithm used.

     - A string-to-key (S2K) specifier, length as defined above.

     - Optionally, the encrypted session key itself, which is decrypted
       with the string-to-key object.

    If the encrypted session key is not present (which can be detected
    on the basis of packet length and S2K specifier size), then the S2K
    algorithm applied to the passphrase produces the session key for
    decrypting the file, using the symmetric cipher algorithm from the
    Symmetric-Key Encrypted Session Key packet.

    If the encrypted session key is present, the result of applying the
    S2K algorithm to the passphrase is used to decrypt just that
    encrypted session key field, using CFB mode with an IV of all zeros.
    The decryption result consists of a one-octet algorithm identifier
    that specifies the symmetric-key encryption algorithm used to
    encrypt the following Symmetrically Encrypted Data packet, followed
    by the session key octets themselves.

    Note: because an all-zero IV is used for this decryption, the S2K
    specifier MUST use a salt value, either a Salted S2K or an
    Iterated-Salted S2K.  The salt value will ensure that the decryption
    key is not repeated even if the passphrase is reused.
    """
    __ver__ = 4

    @property
    def symalg(self):
        return self.s2k.encalg

    def __init__(self):