In this paper, we analyze the security of HMAC and NMAC, both of which are hash-based message authentication codes. We present distinguishing, forgery, and partial key recovery attacks on HMAC and NMAC using collisions of MD4, MD5, SHA-0, and reduced SHA-1. Our results demonstrate that the strength of a cryptographic scheme can be greatly weakened by the insecurity of the underlying hash function.

Identity-based encryption (IBE) allows one party to send ciphered messages to another using an arbitrary identity string as an encryption key. Since IBE does not require prior generation and distribution of keys, it greatly simplifies key management in public-key cryptography. Although the concept of IBE was introduced by Shamir in 1981, constructing a practical IBE scheme remained an open prob...

Mobile code systems are technologies that allow applications to move their code, and possibly the corresponding state, among the nodes of a wide-area network. Code mobility is a exible and powerful mechanism that can be exploited to build distributed applications in an Internet scale. At the same time, the ability to move code to and from remote hosts introduces serious security issues. These i...

At CRYPTO 2003, Rubin and Silverberg introduced the concept of torus-based cryptography over a finite field. We extend their setting to the ring of integers modulo N . We so obtain compact representations for cryptographic systems that base their security on the discrete logarithm problem and the factoring problem. This results in smaller key sizes and substantial savings in memory and bandwidt...

Electronic communication has become one of the main pillars of modern society and their ongoing boom requires the development of new methods and techniques to secure data transmission. This has been the goal since the onset of cryptography in ancient times. Cryptography may be defined as the art of writing (encryption) and deciphering (decryption) messages in code in order to ensure their confi...

In this paper we present rank-based cryptogra­ phy and discuss its interest relatively to other post-quantum families of cryptosystems like for in­ stance code (Hamming)-based cryptography or lattice (Euclidean)-based cryptography. We also survey re­ cent interesting results for this metric and show that rank based cryptography has many advantages and is a credible alternative to classical cryp...

Code-based cryptography (CBC) is one of the most prominent post-quantum alternatives to conventional cryptography. Although quantumresistant and several times faster than its conventional counterparts, CBC is not widely deployed in practice. This is mostly due to its huge public-key sizes of several kilobytes. In this thesis, two different approaches to overcome this problem are introduced. One...

Cryptography based on the theory of error correcting codes and lattices has received a wide attention in the last years. Shor’s algorithm showed that in a world where quantum computers are assumed to exist, number theoretic cryptosystems are insecure. Therefore, it is important to design suitable, provably secure post-quantum signature schemes. Code-based public key cryptography has the charact...