I've got an EC key pair. I need to save it using DEREncodePublicKey
(http://www.cryptopp.com/docs/ref/class_d_l___public_key___e_c.html).
Crypto++ writes out the full domain parameters:
$ openssl ec -in ec-pub-xxx.pem -text -noout -pubin
read EC key
Private-Key: (256 bit)
pub:
04:3e:cb:d0:fb:9d:8d:30:fd:69:a0:42:d8:b6:93:
47:8b:b2:64:2e:bd:d8:27:70:f4:80:85:24:3d:3a:
a5:23:a8:db:05:67:da:62:66:53:ee:a1:31:f8:0c:
7f:45:23:72:d0:89:97:c3:90:cb:d5:15:c9:1c:13:
86:5d:a6:8d:80
Field Type: prime-field
Prime:
00:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:
ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:fe:ff:
ff:fc:2f
A: 0
B: 7 (0x7)
...
But I need the OID of the curve (i.e., the named curve), and not the domain
parameters:
$ openssl ec -in ec-pub.pem -text -noout -pubin
read EC key
Private-Key: (256 bit)
pub:
04:3e:cb:d0:fb:9d:8d:30:fd:69:a0:42:d8:b6:93:
47:8b:b2:64:2e:bd:d8:27:70:f4:80:85:24:3d:3a:
a5:23:a8:db:05:67:da:62:66:53:ee:a1:31:f8:0c:
7f:45:23:72:d0:89:97:c3:90:cb:d5:15:c9:1c:13:
86:5d:a6:8d:80
ASN1 OID: secp256k1
The two outputs above are really the same key. The program read a public
key written by OpenSSL (ec-pub.pem), and then saved the key using Crypto++
(ec-pub-xxx.pem). So the above is the result of attempting to round trip
the key.
Does anyone know how to make Crypto++ use the named curve rather than the
domain parameters?
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