On Fri, Apr 28, 2006, Hailin Wu wrote: > Hello, > > I heard of a recent requirement to use much larger public exponent e, > which is different from > the traditional value of either 65537 or 3. > > The requirement has been stated by CESG which is a part of Government > Communications Headquarters (GCHQ). > Given GCHQ's reputation, I suspect that they must have found some security > weakness in using 65537 as the > public exponent. > > It appears that "openssl genrsa" will use either 3 or 65537 as its > public exponent, > and the internal RSA_generate_key(..) has one input for e_value, > meaning we have to provide an e_value. > > Is this a known OpenSSL limitation? > > Is there any way to generate and use a larger e_value such as one that is > 160 bit > long in OpenSSL? >
It can't currently be done with genrsa but the API supports it. It *can* be done with the very latest OpenSSL 0.9.9 snapshots and the genpkey utility for example: openssl genpkey -algorithm rsa -pkeyopt rsa_keygen_pubexp:0x12345 any version of OpenSSL can use such a key. Any value can be used as the argument to that option. BTW CryptoAPI will have problems with thsi requirement because the public exponent value is assumed to fit in 32 bits all over the place. Steve. -- Dr Stephen N. Henson. Email, S/MIME and PGP keys: see homepage OpenSSL project core developer and freelance consultant. Funding needed! Details on homepage. Homepage: http://www.drh-consultancy.demon.co.uk ______________________________________________________________________ OpenSSL Project http://www.openssl.org Development Mailing List openssl-dev@openssl.org Automated List Manager [EMAIL PROTECTED]
