PKCS1_OAEP.py 文件源码

def encrypt(self, message):
        """Produce the PKCS#1 OAEP encryption of a message.

        This function is named ``RSAES-OAEP-ENCRYPT``, and is specified in
        section 7.1.1 of RFC3447.

        :Parameters:
         message : string
                The message to encrypt, also known as plaintext. It can be of
                variable length, but not longer than the RSA modulus (in bytes)
                minus 2, minus twice the hash output size.

        :Return: A string, the ciphertext in which the message is encrypted.
            It is as long as the RSA modulus (in bytes).
        :Raise ValueError:
            If the RSA key length is not sufficiently long to deal with the given
            message.
        """
        # TODO: Verify the key is RSA

        randFunc = self._key._randfunc

        # See 7.1.1 in RFC3447
        modBits = Crypto.Util.number.size(self._key.n)
        k = ceil_div(modBits,8) # Convert from bits to bytes
        hLen = self._hashObj.digest_size
        mLen = len(message)

        # Step 1b
        ps_len = k-mLen-2*hLen-2
        if ps_len<0:
            raise ValueError("Plaintext is too long.")
        # Step 2a
        lHash = self._hashObj.new(self._label).digest()
        # Step 2b
        ps = bchr(0x00)*ps_len
        # Step 2c
        db = lHash + ps + bchr(0x01) + message
        # Step 2d
        ros = randFunc(hLen)
        # Step 2e
        dbMask = self._mgf(ros, k-hLen-1)
        # Step 2f
        maskedDB = strxor(db, dbMask)
        # Step 2g
        seedMask = self._mgf(maskedDB, hLen)
        # Step 2h
        maskedSeed = strxor(ros, seedMask)
        # Step 2i
        em = bchr(0x00) + maskedSeed + maskedDB
        # Step 3a (OS2IP), step 3b (RSAEP), part of step 3c (I2OSP)
        m = self._key.encrypt(em, 0)[0]
        # Complete step 3c (I2OSP)
        c = bchr(0x00)*(k-len(m)) + m
        return c