Hi,
My program needs to sign and verify a message. The message is very small
like 64 bytes only. Do I still need to create a message digest (Hash)
for this? Or hashing is just needed to reduce data size?

In other words, if I encrypt my message with private key to create
signature. And send it over to decrypt it with public key to verify by
comparing orignal message and decrypted. Will there be any threat to my
private key? Can someone know my private key provided plain message and
its signature info?

remember, the formula is,
s = m ^ d MOD N
and in this case s, m and N are known.

please inform, thanks.
susan