def crypto_box_open_afternm(ciphertext, nonce, k):
"""
Decrypts and returns the encrypted message ``ciphertext``, using the shared
key ``k`` and the nonce ``nonce``.
:param ciphertext: bytes
:param nonce: bytes
:param k: bytes
:rtype: bytes
"""
if len(nonce) != crypto_box_NONCEBYTES:
raise exc.ValueError("Invalid nonce")
if len(k) != crypto_box_BEFORENMBYTES:
raise exc.ValueError("Invalid shared key")
padded = (b"\x00" * crypto_box_BOXZEROBYTES) + ciphertext
plaintext = ffi.new("unsigned char[]", len(padded))
res = lib.crypto_box_open_afternm(plaintext, padded, len(padded), nonce, k)
ensure(res == 0,
"An error occurred trying to decrypt the message",
raising=exc.CryptoError)
return ffi.buffer(plaintext, len(padded))[crypto_box_ZEROBYTES:]
def crypto_box_open_afternm(ciphertext, nonce, k):
"""
Decrypts and returns the encrypted message ``ciphertext``, using the shared
key ``k`` and the nonce ``nonce``.
:param ciphertext: bytes
:param nonce: bytes
:param k: bytes
:rtype: bytes
"""
if len(nonce) != crypto_box_NONCEBYTES:
raise exc.ValueError("Invalid nonce")
if len(k) != crypto_box_BEFORENMBYTES:
raise exc.ValueError("Invalid shared key")
padded = (b"\x00" * crypto_box_BOXZEROBYTES) + ciphertext
plaintext = ffi.new("unsigned char[]", len(padded))
res = lib.crypto_box_open_afternm(
plaintext, padded, len(padded), nonce, k)
ensure(res == 0, "An error occurred trying to decrypt the message",
raising=exc.CryptoError)
return ffi.buffer(plaintext, len(padded))[crypto_box_ZEROBYTES:]