Abstract:
Tweakable ciphers are a relatively new and interesting area in the field of
cryptology. It is a current subject and considerable researches have been carried out on the
topic. It is a step further in the field of cryptographic tools. Many encryption schemes have
been developed using the block ciphers which can be implemented on fixed length inputs
and in some implementation cases can result in expansion of length. Tweakable
Enciphering Schemes aim at developing a system which can handle arbitrary input lengths
and ensures length preservation and also provides variability of the ciphertexts.
A lot many schemes are present in this field. All the schemes have their own
benefits and limitations. In this context it is important that an analysis of these schemes is
carried out to discover their appropriateness for different applications. Therefore the
schemes have been analysed in terms of their security and efficiency. The idea of
tweakable enciphering schemes is further studied and the option of having such schemes
that only use the encryption function for both the encryption and decryption routines have
been studied. Moreover the idea was further explored to use stream ciphers in place of the
block ciphers. The feasibility of such structures has been studied in detail.
The schemes can be used for disk encryption where the variability is ensured by
the tweak. In this context the applicability and feasibility of various schemes for disk
encryption is studied. The schemes have been analysed in terms of their speed and
hardware requirements for this application. The standard for disk encryption IEEE Std
1619 has also been studied and the different schemes available for disk encryption have
been analysed accordingly.
Some modified structures are also proposed. They have been analysed in terms of
their security and efficiency for implementation in disk encryption. These schemes have
been proved to be compatible with the existing schemes in terms of their security and disk
encryption implementation and can be used effectively for in place of the existing
schemes.
