Daniel Bleichenbacher

Daniel Bleichenbacher (born 1964) is a Swiss cryptographer, previously a researcher at Bell Labs, and currently employed at Google. He received his Ph.D. from ETH Zurich in 1996 for contributions to computational number theory, particularly concerning message verification in the ElGamal and RSA public-key cryptosystems.

In 1998, Daniel Bleichenbacher demonstrated a practical attack against systems using RSA encryption in concert with the PKCS#1 v1 encoding function, including a version of the Secure Socket Layer (SSL) protocol used by thousands of web servers at the time. This attack was the first practical reason to consider adaptive chosen-ciphertext attacks.

In 2006 at a rump session at CRYPTO, Bleichenbacher described a "pencil and paper"-simple attack against RSA signature validation as implemented in common cryptographic toolkits. Both OpenSSL and the NSS security engine in Firefox were later found to be vulnerable to the attack, which would allow an attacker to forge the SSL certificates that protect sensitive websites.