This tool (available for Windows, MacOSX and Linux) enables you to convert an RSA private key from an SFM format (Straightforward Method, containing the modulus, private exponent and public exponent) to the CRT format. It also supports converting keys from CRT to SFM. Moreover, you are free to choose the endianess of the input and the output values.

Mathematical Background

The algorithm to compute the prime factorization of the RSA modulus using the public and the private exponents is based on the idea presented by Dan Boneh on his paper "Twenty Years of Attacks on the RSA Cryptosystem".

You can get the PDF of this paper by clicking here.