Asymmetric Key sizes

[Parker Tom TA]

Although a lot is being said about the shrinking level of security offered
by various symmetric key sizes, with 56 bits coming in for a lot of stick,
haven't seen anything lately on asymmetric attacks. Has anyone any
information on the latest successful attack position on asymmetric keys, RSA
in particular? How secure is 512 bits considered now, and why? What's the
current recommended key size? Has anything been published that is later than
the now rather old (January 1996) "Report by the Ad Hoc Group of
Cryptographers and Computer Scientists"?

Thanks in advance,

Tom Parker
tom.a.parker@icl.com