This paper studies how to build a 2n-bit block cipher which is hard to distinguish from a truly random permutation against attacks with q ≈ 2 queries, i.e., birthday attacks. Unlike previous approaches using pseudorandom functions, we present a simple and efficient proposal using a tweakable block cipher as an internal module. Our proposal is provably secure against birthday attacks, if underly...

We present a new 128-bit block cipher called Camellia. Camellia supports 128-bit block size and 128-, 192-, and 256-bit keys, i.e. the same interface specifications as the Advanced Encryption Standard (AES). Efficiency on both software and hardware platforms is a remarkable characteristic of Camellia in addition to its high level of security. It is confirmed that Camellia provides strong securi...

We analyze the security of elastic block ciphers in general to show that an attack on an elastic version of block cipher implies a polynomial time related attack on the fixed-length version of the block cipher. We relate the security of the elastic version of a block cipher to the fixed-length version by forming a reduction between the versions. Our method is independent of the specific block c...

We present a new 128-bit block cipher called Camellia. Camellia supports 128-bit block size and 128-, 192-, and 256-bit keys, i.e. the same interface specifications as the Advanced Encryption Standard (AES). Efficiency on both software and hardware platforms is a remarkable characteristic of Camellia in addition to its high level of security. It is confirmed that Camellia provides strong securi...

A block cipher, such as the DES cipher, is used to encrypt binary plaintext in discrete blocks of length n using a key of length m, to form ciphertext blocks of length n. A block cipher is said to satisfy the strict key avalanche criterion if a one bit change in the key causes on the average one half of the ciphertext bit positions to change. In this paper the importance of the strict key avala...

Image encryption has become an important application aspect of information security. Most attempts are focused on increasing the security aspect, quality resulting image, and time consumed. On other hand, dealing with color image under spatial domain in this filed is considered as another challenge added to proposed method that make it sensitivity difficulty. The aims encode a by main component...

The idea of double block length hashing is to construct a compression function on 2n bits using a block cipher with an n-bit block size. All optimally secure double length hash functions known in the literature employ a cipher with a key space of double block size, 2n-bit. On the other hand, no optimally secure compression functions built from a cipher with an n-bit key space are known. Our wor...

Given a block cipher of length L Cook’s elastic cipher allows to encrypt messages of variable length from L to 2L. Given some conditions on the key schedule, Cook’s elastic cipher is secure against any key recovery attack if the underlying block cipher is, and it achieves complete diffusion in at most q+1 rounds if the underlying block cipher achieves it in q rounds. We extend Cook’s constructi...

Title of dissertation: IMPROVING THE ROUND COMPLEXITY OF IDEAL-CIPHER CONSTRUCTIONS Aishwarya Thiruvengadam, Doctor of Philosophy, 2017 Dissertation directed by: Professor Jonathan Katz Department of Computer Science Block ciphers are an essential ingredient of modern cryptography. They are widely used as building blocks in many cryptographic constructions such as encryption schemes, hash funct...