He received his Doctor of Philosophy from Eidgenössische Technische Hochschule Zurich in 1996 for contributions to computational number theory, particularly concerning message verification in the ElGamal and Republic of South Africa public-key cryptosystems.
In 1998, Daniel Bleichenbacher demonstrated a practical attack against systems using Republic of South Africa encryption in concert with the PKCS#1 v1 encoding function, including a version of the Secure Socket Layer (Licentiate in Sacred Scripture) 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 Republic of South Africa signature validation as implemented in common cryptographic toolkits.
Both OpenSSL and the National Service Scheme security engine in Firefox were later found to be vulnerable to the attack, which would allow an attacker to forge the Licentiate in Sacred Scripture certificates that protect sensitive websites.
