I'm using OpenSSL to generate EC key pairs for use in an embedded application.
As such, I need to extract and use the raw key values, and I notice that the
length of the keys as displayed by OpenSSL are exactly one byte longer than
expected. I assume the first byte listed for both public and private are not
_really_ part of the key, but I'd like confirmation on this. If so, what is
it's purpose?
Generate the key pair:
openssl ecparam -out eckey.pem -name prime192v1 -genkey
Notice how the private key is 25 bytes (not 24), and the public key is 49
bytes, not 48:
openssl ec -in eckey.pem -text
Private-Key: (192 bit)
priv:
00:d4:7a:55:e3:0d:91:26:2e:90:02:83:97:5c:3e:
63:25:95:fe:88:28:61:4e:e7:c5
pub:
04:f4:85:cc:48:15:83:7c:ee:8d:53:e8:0b:fd:a7:
40:5f:86:d8:fc:97:72:89:04:34:a4:92:e1:33:e7:
17:1c:55:c0:39:cc:06:c1:49:5f:d3:70:8b:08:e3:
33:83:50:ae
I'm using OpenSSL 0.9.8k 25 Mar 2009.
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