Hello Dave, Am really thankful to you. I am unaware that i2d_EC_PUBKEY() or i2d_xxxxx function will move the pointer to after the encoded data. Due to which am seeing unexpected data. Based on your reply, i tried to print the data from the memory address which i allocated. Now the data is exactly same as what i inputted through d2i_PUBKEY(). This resolves my current issue. Once again, thanks alot. Rajeswari. On Fri, Feb 13, 2015 at 2:36 AM, Dave Thompson <dthompson at prinpay.com> wrote: > > From: openssl-users On Behalf Of Rajeswari K > > Sent: Thursday, February 12, 2015 00:40 > > > I have a query on d2i_PUBKEY() and i2d_PUBKEY(). > > > i have a EC public key in form of character buffer. > > Have inputted this character buffer to d2i_PUBKEY() and got EVP_PKEY > format EC key. > > To be exact, a byte (or even more exact octet) buffer. In C > (and C++ and ObjC) it's type 'char[]' or better 'unsigned char[]', > but the values do not and often cannot represent *characters&. > > > Now i tried to input this EVP_PKEY to i2d_PUBKEY() to compare will i get > > exactly same data which i gave as input to d2i_PUBKEY(). > > > But i see that the outputs are completely different. > > > i2d_PUBKEY() is leaving lots of 0's at the o/p buffer. > > > 0 > > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > FD 1 10 DF AB 12 34 CD 0 6F 0 0 0 0 1 83 > > F 8B AF D8 D ................................................ > > You must be doing something wrong. Probably the most common is, > are you looking at the beginning of the buffer? Remember that after > calling i2d_whatever, the pointer you give it is moved to point > *after* the encoded data, at unused and often junk memory. > > If that's not it, reduce your code to the minimum that shows the > problem, post it, and identify the version and build you are using. > > > My goal is, to get complete EC public key in form of asn1 der > > encoded from EC_KEY structure. > > > I tried to use i2d_EC_PUBKEY() and i20_ECPublickey(). <snip> > > Note that PUBKEY is the X.509 SPKI format: it contains an > AlgorithmIdentifier identifying the algorithm and the curve, > *and* the public key value (a point) embedded in a bitstring, > all combined into an ASN.1 structure and DER encoded. > > i2o_ECPublicKey (letter o not zero) uses a special non-ASN1 > non-DER encoding that contains *only* the point. > > > _______________________________________________ > openssl-users mailing list > To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mta.openssl.org/pipermail/openssl-users/attachments/20150213/9aad3128/attachment-0001.html>
