I'm working on a system where I need to sign some data using an ECC private key and share the data and signature over a BLE ADV packet. Since an ADV packet is limited in space, I can't use a full ECDSA signature as the output is too large. As far as I understand, you can't readily truncate an ECDSA signature as you can with AES.
As an alternative, I am considering simply encrypting the data I need to sign using the private key and provide the plaintext-ciphertext pair as a way to communicate to the public key holder that the data was generated from a trusted source (holder of private key).
I know that under other cryptographic systems, this is not advisable as is it exposes the system to a known plaintext attack. I cannot find any information as to whether elliptic curve cryptography is vulnerable to this. I have seen some authentication schemes that suggest doing something like this instead of using signatures.
Is it safe to expose both the plaintext and ciphertext data to an attacker using ECC? Is there another method of signing data with ECC private keys that could yield a smaller signature or allow for truncation of the signature? I need to limit this signature to ~16 bytes or so. I would use a smaller key size but none of the recommended curves use 64 bit signatures which makes sense.