Research On The Block Cipher Mode Of Operation

With the proposition of advanced encryption standard (AES), the block cipher mode of operation becomes a popular topic again. This dissertation reviews the research actuality and significance of mode of operation, designs series of encryption mode and big block cipher mode, analyzes sufficiently their capability. We attack the mode of CFB, double CBC, double CFB et.al under the error oracle attack model.In order to improve the security of mode of operation, a masked ECB mode of operation was constructed with the Gray code to mask the plaintext. Desirable properties of the new scheme include: the ability to encrypt a bit string of arbitrary length into a ciphertext of minimal length; the ability to cover-up the plaintext data mode; provable security. Subsequently, the security of the scheme was analyzed in the sense of reduction-based cryptography, investigation shows that the new scheme is left-or-right indistinguishable against chosen-plaintext attack (LOR-CPA) secure if the underlying block cipher is a pseudorandom permutation.As a basic mode of operation, CBC was proved that it is secure under the standard attack model, but it is not secure under the adaptive attack model. The attacker can destroy its semantic security by fewer queries. The reason is that the last output concerns the next input very nearly. In order to resist such attack, we introduce the gray code and obtain a new mode CBC~+ which is security against adaptive adversary.In order to improve the efficiency and economize cost, the four round MISTY-type and the three round dual MISTY-type transformation are optimized by replacing the first round pseudorandom permutation with XOR-universal permutation and employing identical pseudorandom permutation in the second and the third round. Thus the running time is shortened and the number of keys is saved by reducing the number of...