The Multiplicative-to-Additive (MtA) protocol is an essential building block for secure multi-party computation, particularly within threshold ECDSA schemes. It leverages the Paillier encryption scheme, an additively homomorphic cryptosystem, to enable two parties to convert a product of their secret shares into a sum of new shares without ever revealing their individual values. This is achieved through a secure, multi-round exchange of encrypted shares and range proofs, which are zero-knowledge proofs used to prevent cheating. By converting multiplicative shares to additive ones, MtA provides a fundamental mechanism for distributed, confidential computations, underpinning the security of advanced threshold cryptography.