I have been trying to generate keys for a ECDSA system that uses a sect163k1 key
pair.
In generating some of the key sets, I notice that the printed length of the keys
differ when using the -text command option. Since openssl is displaying a 163
bits in a byte-wise display, I am trying to figure out where the padding bits
are
applied?
For example:
~$ sudo openssl ecparam -genkey -name sect163k1 -out testkey1.pem
~$ sudo openssl ec -text -in testkey1.pem
read EC key
Private-Key: (163 bit)
priv:
00:c4:5c:43:a9:17:57:89:ff:e8:fe:f9:d6:b0:d4:
52:fc:d4:6b:71:98
pub:
04:01:9c:db:21:d7:49:17:cd:c4:93:56:13:e4:07:
c2:af:1b:43:70:a3:b9:03:f1:26:f8:7b:1d:02:69:
21:39:cf:d5:28:ee:3b:44:3c:c5:64:7c:aa
ASN1 OID: sect163k1
writing EC key
-----BEGIN EC PRIVATE KEY-----
MFICAQEEFMRcQ6kXV4n/6P751rDUUvzUa3GYoAcGBSuBBAABoS4DLAAEAZzbIddJ
F83Ek1YT5AfCrxtDcKO5A/Em+HsdAmkhOc/VKO47RDzFZHyq
-----END EC PRIVATE KEY-----
~$ sudo openssl ecparam -genkey -name sect163k1 -out testkey2.pem
~$ sudo openssl ec -text -in testkey2.pem
read EC key
Private-Key: (163 bit)
priv:
65:06:db:ea:88:38:0d:50:37:9e:3a:92:77:15:ca:
3c:76:d0:00:12
pub:
04:07:7d:dd:c1:89:12:75:42:d6:9e:06:79:24:e1:
8b:4a:49:df:57:ac:e2:04:95:a1:2f:b9:dc:a7:8c:
5f:c3:18:a5:a7:9c:fc:9d:be:7f:e6:d7:4e
ASN1 OID: sect163k1
writing EC key
-----BEGIN EC PRIVATE KEY-----
MFICAQEEFGUG2+qIOA1QN546kncVyjx20AASoAcGBSuBBAABoS4DLAAEB33dwYkS
dULWngZ5JOGLSknfV6ziBJWhL7ncp4xfwxilp5z8nb5/5tdO
-----END EC PRIVATE KEY-----
The two private keys are described in a different number of bytes.
Since the 2nd generated private key is shown in 20 bytes i.e. 160 bits, is it
assumed that the MS 3 bits are 0?
How is the public key partitioned? Where are the padding bits added in this
display?
Thanks
Doug Bailey
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