I am working in a very bandwidth restricted environment where I from time to time have the need to distribute public keys. The distribution happens in bit format, so there is no need for encoding, at best I would like all my data "raw".
It is my understanding that the public key, in compressed form, takes up the space of the curve size+1, e.g. 160 bit curve gives 161 bit public key. However, the output from OpenSSL gives me a much larger key size, e.g. 904 bits for the secp160r1 curve. I reckon there must be a lot of metadata involved.
Edit: I removed the "--- Public key starts here ---" etc and that almost cut the file in half ahem. But still there are 60 bytes/480 bits, a lot more than what I would think of as necessary.
Can I somehow reduce this size, getting rid of metadata? For example extract the key components of the signature and reassemble it in a compatible format on the receiver side? I assume DER encoding also adds overhead, but hardly this much?
Here arethe commands I use, in Cygwin:
$ openssl ecparam -out private.pem -name secp160k1 -genkey $ openssl ec -in private.pem -pubout -conv_form compressed -out public.pem