Summation operation between ciphertext

I’m new to homomorphic encryption and I’ve been exploring it by working through some examples in the library. While experimenting with the CKKS scheme, I attempted to perform a summation operation on ciphertexts encrypted using different public keys. However, I encountered errors. I’m curious to know if there’s a way to perform such operations when the ciphertexts don’t share a common key, perhaps in other encryption schemes.

thanks in advance

Perhaps, threshold CKKS (which is implemented in OpenFHE) might be suitable for your use case. In this scheme, multiple parties can encrypt data with their own unique secret key. However, they run a join protocol to generate a common public key. Moreover, decryption is also a joint protocol, where all parties participate in decrypting ciphertexts.