Are Bitcoin signatures currency specific? I am wondering whether signatures for Bitcoin-like currencies are currency specific, or given one program that can sign a Bitcoin raw/JSON transaction one can create valid signatures for other coins as well?

That is to say, if a program takes:


A private key
A pre-contructed raw / JSON transaction


Is the signing process requiring something specific to a given currency, like referencing an address in a different form or using some currency-specific bytes?
All coins use ECDSA to sign transactions in a similar manner, the main difference between most coins is what would constitute a valid signature, typically the first character(s) of a public address (e.g. bitcoin starts with 1 or 3 and litecoin starts with L). Therefore a certain public key could not be used directly to sign a transaction of another coin, with exception to coins such as devcoin, which uses the same address type.

You could write a program which starting from a certain private key, auto-increments until a valid address is found.