def _decrypt_via_rsa_oaep(cipherdict: dict, key: RSA.RsaKey) -> bytes:
"""Decrypt a bytestring with PKCS#1 RSA OAEP (asymmetric algo).
:param cipherdict: list of ciphertext chunks
:param key: private RSA key
:return: the decrypted bytestring"""
_check_asymmetric_key_length_bits(key.size_in_bits())
decipher = PKCS1_OAEP.new(key, hashAlgo=RSA_OAEP_HASHER)
encrypted_chunks = cipherdict["digest_list"]
decrypted_chunks = []
for encrypted_chunk in encrypted_chunks:
decrypted_chunk = decipher.decrypt(encrypted_chunk)
decrypted_chunks.append(decrypted_chunk)
return b"".join(decrypted_chunks)
def _encrypt_via_rsa_oaep(plaintext: bytes, key: RSA.RsaKey) -> dict:
"""Encrypt a bytestring with PKCS#1 RSA OAEP (asymmetric algo).
:param plaintext: the bytes to cipher
:param key: public RSA key
:return: a dict with field `digest_list`, containing bytestring chunks of variable width."""
_check_asymmetric_key_length_bits(key.size_in_bits())
cipher = PKCS1_OAEP.new(key=key, hashAlgo=RSA_OAEP_HASHER)
chunks = split_as_chunks(plaintext,
chunk_size=RSA_OAEP_CHUNKS_SIZE,
must_pad=False,
accept_incomplete_chunk=True)
encrypted_chunks = []
for chunk in chunks:
encrypted_chunk = cipher.encrypt(chunk)
encrypted_chunks.append(encrypted_chunk)
return dict(digest_list=encrypted_chunks)