Ok, can you expain me how ec_compute_key work and specially this last argument. Why its need hash value to calculate the secret key. I need to generate the 56 BYtes shred key.
On 18 December 2012 10:32, Jeffrey Walton <noloa...@gmail.com> wrote: > On Mon, Dec 17, 2012 at 11:50 PM, jeetendra gangele > <gangele...@gmail.com> wrote: >> U mean to say I can generate 64 bytes and then I can ignore last 8 >> bytes? so I will get 56 bytes. >> This value then I have to use as secret key for ECDH > https://www.google.com/#q=truncated+hash > > Be careful of ECDH because its anonymous or non-authenticated. NIST > Special Publication 800-56A, Recommendation for Pair-Wise Key > Establishment Schemes Using Discrete Logarithm Cryptography, might > help guide you. > > Jeff > >> On 18 December 2012 09:57, Jeffrey Walton <noloa...@gmail.com> wrote: >>> On Mon, Dec 17, 2012 at 11:16 PM, jeetendra gangele >>> <gangele...@gmail.com> wrote: >>>> Hi, >>>> Do we have support for 448 bit hash value generation in openssl.? >>>> I looked into the header file and I did not find functiobn related to that. >>>> >>>> Actually I need to compute shared key for ecdh and that should be 56 Bytes >>>> long. >>>> I could genearte the 20 byte 32 bytes but I need 56 bytes only. >>> 448 bits is 56 bytes. You will have to use a smaller hash and iterate >>> in a KDF-like fashion; or a larger hash and truncate. > ______________________________________________________________________ > OpenSSL Project http://www.openssl.org > User Support Mailing List openssl-users@openssl.org > Automated List Manager majord...@openssl.org ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager majord...@openssl.org
