I'm working on a encryption system where each party can store exactly a single ElGamal private key in a device. This is a hardware limit. The system must be expanded to support signatures and encryption.
Can each party use the same key-pair for both schemes?
I know that encryption/signature key lifetimes and security key-lengths may be different, but this would not pose any serious risk to our system.
So the question can be restated as: Are there passive or active attacks (e.g. algebraic, chosen-plaintext/ciphertext) that are specifically targeted at users sharing ElGamal Encryption/Signature key-pairs?