Timing based RSA key recovery

[tomato42]

Add tests to verify that extraction of private key based on private key operations is not possible.

See:

• D. Brumley, D. Boneh Remote Timing Attacks are Practical: https://crypto.stanford.edu/~dabo/pubs/papers/ssl-timing.pdf
• Paul C. Kocher Timing Attacks on Implementations of Diffie-Hellman, RSA, DSS and Other Systems: https://link.springer.com/content/pdf/10.1007%2F3-540-68697-5_9.pdf
• Werner Schindler A timing attack against RSA with the Chinese remainder theorem: https://tls.mbed.org/public/WSchindler-RSA_Timing_Attack.pdf