This is the scheme of a parallelizable block cipher mode of operation:
- $IV$ is the initialization vector.
- $BN$ is the zero-based index number of a block in a stream of data.
- $BT$ is the tweak that is used in the encryption process of each block.
- $K$ is the key.
- $PT$ is a plaintext block.
- $CT$ is a ciphertext block.
Encryption and decryption are as follows:
- $BT = IV \boxplus BN$
- $CT = \mathrm{Encrypt}(K, PT \oplus BT)$
- $PT = \mathrm{Decrypt}(K, CT) \oplus BT$
What is obvious to me about this scheme:
- It is parallelizable.
- It does not suffer from the drawbacks of ECB mode.
- There is no cascading effect as seen in CBC, PCBC, and OFB modes of operation.
Are there any security drawbacks with this scheme?
Update: I've considered the criticism and now $BT = \mathrm{Encrypt}(K, IV \boxplus BN)$. What impact does this have on the security?