David Naccache is a cryptographer, currently a professor at the Pantheon-Assas Paris II University and member of the École normale supérieure

École normale supérieure

An école normale supérieure or ENS is a type of publicly funded higher education in France. A portion of the student body who are French civil servants are called Normaliens....

's Computer Laboratory. He is also a visiting professor at Royal Holloway University of London's Information Security Group. He received his Ph.D.

Doctor of Philosophy

Doctor of Philosophy, abbreviated as Ph.D., PhD, D.Phil., or DPhil , in English-speaking countries, is a postgraduate academic degree awarded by universities...

 in 1995 from the École nationale supérieure des télécommunications

École Nationale Supérieure des Télécommunications

Télécom ParisTech is one of the most prestigious and selective grandes écoles in France and one of the finest institutions in the field of Telecommunications...

. Naccache's most notable work includes the design of the SHACAL

SHACAL

SHACAL-1 is a 160-bit block cipher based on SHA-1, and supports keys from 128-bit to 512-bit. SHACAL-2 is a 256-bit block cipher based upon the larger hash function SHA-256....

 block cipher

Block cipher

In cryptography, a block cipher is a symmetric key cipher operating on fixed-length groups of bits, called blocks, with an unvarying transformation. A block cipher encryption algorithm might take a 128-bit block of plaintext as input, and output a corresponding 128-bit block of ciphertext...

s with Helena Handschuh as well as substantial work in public-key cryptography

Public-key cryptography

Public-key cryptography refers to a cryptographic system requiring two separate keys, one to lock or encrypt the plaintext, and one to unlock or decrypt the cyphertext. Neither key will do both functions. One of these keys is published or public and the other is kept private...

, including the cryptanalysis

Cryptanalysis

Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...

 of digital signature

Digital signature

A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit...

 schemes. Together with Jacques Stern

Jacques Stern

Jacques Stern is a cryptographer, currently a professor at the École Normale Supérieure, where he is Director of the Computer Science Laboratory. He received the 2006 CNRS Gold Medal...

 he designed the similarly named but very distinct Naccache-Stern cryptosystem

Naccache-Stern cryptosystem

Note: this is not to be confused with the Naccache–Stern knapsack cryptosystem.The Naccache–Stern cryptosystem is a homomorphic public-key cryptosystem whose security rests on the higher residuosity problem...

 and Naccache-Stern knapsack cryptosystem

Naccache-Stern knapsack cryptosystem

Note: this is not to be confused with the Naccache–Stern cryptosystem based on the higher residuosity problem.The Naccache–Stern Knapsack Cryptosystem is an atypical public-key cryptosystem developed by David Naccache and Jacques Stern in 1997. This cryptosystem is deterministic, and hence is not...

.

In 2004 David Naccache and Claire Whelan, then employed by Gemplus International

Gemplus International

Acquired by the Texas Pacific Group in 2000, Luxemburg-based Gemplus International SA was a provider of smart cards and related technologies, until its June 2, 2006 merger with rival Axalto; the combined entity is known as Gemalto....

, used image processing

Image processing

In electrical engineering and computer science, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame; the output of image processing may be either an image or, a set of characteristics or parameters related to the image...

 techniques to uncover redacted

Redaction

Redaction is a form of editing in which multiple source texts are combined and subjected to minor alteration to make them into a single work. Often this is a method of collecting a series of writings on a similar theme and creating a definitive and coherent work...

 information from the declassified 6 August 2001 President's Daily Brief

President's Daily Brief

The President's Daily Brief , sometimes incorrectly referred to as the President's Daily Briefing or the President's Daily Bulletin, is a top-secret document produced each morning for the President of the United States...

 Bin Ladin Determined To Strike in US. They also demonstrated how the same process could be applied to other redacted documents.

External links

• David Naccache's personal page at École normale supérieure
  École normale supérieure
  An école normale supérieure or ENS is a type of publicly funded higher education in France. A portion of the student body who are French civil servants are called Normaliens....