"There is a good chance that large quantum computers can be built within the next 20 years.  This would be a nightmare for IT security if there are no fully developed, implemented, and standardized post-quantum signature schemes."

Prof. Johannes Buchmann, et al, “Post-Quantum Signatures”, Oct 2004, Technische Universität Darmstadt

“So the threat to cryptography is well understood due to work by Peter Shor and others. A symmetric algorithm like AES or others standard crypto processes is cut (of) key-size in half, which is a dramatic reduction. ... For key management purposes, against the RSA and the Diffie-Hellman and stuff, they flat-line under a quantum computer.”

Brian Snow, Former Technical Director of the US National Security Agency (NSA), Public Key Cryptography 30th Anniversary Conference, Dec 2006

"In the medium term, we need to be prepared for the eventuality that large quantum computers could be built: this would require an upgrade of most symmetric cryptographic algorithms and a completely new generation of public-key algorithms."

SecurIST, “D3.3 – ICT Security & Dependability Research beyond 2010: Final Strategy”, January 2007