In the past there have been a few proposals to use asymmetric cryptosystems, typically RSA, like symmetric ones by keeping the public key secret, the idea behind this being that if the public key isn't known then there isn't anything for an attacker to factor or otherwise attack. Turns out that doing this isn't secure:
http://eprint.iacr.org/2012/588 Breaking Public Keys - How to Determine an Unknown RSA Public Modulus Hans-Joachim Knobloch [...] We show that if the RSA cryptosystem is used in such a symmetric application, it is possible to determine the public RSA modulus if the public exponent is known and short, such as 3 or F4=65537, and two or more plaintext/ciphertext (or, if RSA is used for signing, signed value/signature) pairs are known. Peter. _______________________________________________ cryptography mailing list cryptography@randombit.net http://lists.randombit.net/mailman/listinfo/cryptography
