def gostr3410_key_transport(cek_enc: bytes, mac: bytes, ukm: bytes, pub_ephemeral: bytes) -> str:
    """Создание структуры GostR3410-KeyTransport

    :param cek_enc: Зашифрованный сессионный ключ симметричного шифрования данных
    :type cek_enc: bytes
    :param mac: MAC сессионного ключа
    :type mac: bytes
    :param ukm: UserKeyMaterial, сгенерированный случайно
    :type ukm: bytes
    :param pub_ephemeral: Публичный ключ эфемерной пары, сгенерированный на основе закрытого ключа
    :type pub_ephemeral: bytes
    :return: Структура GostR3410-KeyTransport - байт-код в DER-формате, закодированный в Base64
    :rtype: str
    """

    cek_enc_octet = Gost2814789Key(cek_enc)
    mak_octet = Gost2814789MAC(mac)

    encrypted_key = Gost2814789EncryptedKey()
    encrypted_key['encryptedKey'] = cek_enc_octet
    encrypted_key['macKey'] = mak_octet

    algorithm = AlgorithmIdentifier()
    algorithm['algorithm'] = ObjectIdentifier('1.2.643.7.1.1.1.1')
    algorithm['parameters'] = Any(Null())

    pub_ephemeral_bitstring = BitString(pub_ephemeral)

    ephemeralPublicKey = SubjectPublicKeyInfo(impl=tag_ctxc(0), optional=True)
    ephemeralPublicKey['algorithm'] = algorithm
    ephemeralPublicKey['subjectPublicKey'] = pub_ephemeral_bitstring

    ukm_octet = OctetString(ukm)
    transport_parameters = GostR34102001TransportParameters(impl=tag_ctxc(0), optional=True)
    transport_parameters['encryptionParamSet'] = ObjectIdentifier('1.2.643.7.1.2.1.1.2')
    transport_parameters['ephemeralPublicKey'] = ephemeralPublicKey
    transport_parameters['ukm'] = ukm_octet

    structure = GostR3410KeyTransport()
    structure['sessionEncryptedKey'] = encrypted_key
    structure['transportParameters'] = transport_parameters

    b_structure = structure.encode()
    base64_structure = b64encode(b_structure).decode('utf-8')

    return base64_structure

SEQUENCE {
   SEQUENCE {
      OCTETSTRING a0e8c65197af5fe2b0fe38519f51246d9c8aa1d3dc93cd4dca0ce5ab9f1a5b95
      OCTETSTRING 188e9b08
   }
   [0] {
      OBJECTIDENTIFIER 1.2.643.7.1.2.1.1.2
      [0] {
         SEQUENCE {
            OBJECTIDENTIFIER 1.2.643.7.1.1.1.1
            NULL 
         }
         BITSTRING 0xcb1f988917de18f08e78f989d459d976e1a4771c207b7b77d04996d89e7416ab4d3558612f56d2238701c098bd3e1cfd34ab3d3bbf5caf1e3a1798f4a1f6d519 : 0 unused bit(s)
      }
      OCTETSTRING b3334e27c5c76f7d
   }
}

GostR3410KeyTransport SEQUENCE[
    sessionEncryptedKey: Gost2814789EncryptedKey SEQUENCE[
        encryptedKey: Gost2814789Key OCTET STRING 32 bytes 07094633121737be3dc2a6c6049e67a875e3c876efdd922e68ccc7c25bf580cd;
        macKey: Gost2814789MAC OCTET STRING 4 bytes 9e09e950
    ];
    transportParameters: [0] GostR34102001TransportParameters SEQUENCE OPTIONAL[
        encryptionParamSet: OBJECT IDENTIFIER 1.2.643.7.1.2.5.1.1;
        ephemeralPublicKey: [0] SubjectPublicKeyInfo SEQUENCE OPTIONAL[
            algorithm: AlgorithmIdentifier SEQUENCE[
                algorithm: OBJECT IDENTIFIER 1.2.643.7.1.1.6.1;
                parameters: ANY NULL OPTIONAL
            ];
            subjectPublicKey: BIT STRING 512 bits b785c90eb06160061276ac0ebed257bf680f74ccf6f0476c67ef71922d65f95781648b0097283dfa11e5a1303ac9a00dc19e2b1aa40a3027230973524634b665
        ];
        ukm: OCTET STRING 8 bytes 91275a6435733816
    ]
]