Security estimates for 512-bit RSA

We address the short-term security offered by the use of a 512-bit RSA modulus. Following the tremendous improvements to the practicality of the generalized number field sieve, it must be expected that the 512-bit RSA number will have been factored. However, for those fielded systems which use 512-bit RSA, what are the implications? Some systems may well continue using 512-bit RSA long after one particular 512-bit RSA number has been factored. In this note, we present data which might provide answers to questions about the continuing use of a 512-bit RSA modulus