Import of encrypted keys to a secure multi-party computation system

A method at a second device, comprising:

• executing, with a first device, a secure computation protocol that uses an input of a second decryption key share of a decryption key and a ciphertext corresponding to an encryption of a signing key, wherein execution of the secure computation protocol results in output, to the second device, a second signing key share of the signing key;
• receiving information indicative of a first public key share of a public key and a result of an execution of a zero-knowledge proof from the first device;
• verifying that the public key is equal to a summation of the first public key share and a first product, the first product being of the second signing key share of the signing key and a generator function;
• verifying that the result of the execution of the zero-knowledge proof is valid such that the first public key share corresponds to a second product, the second product being of a first signing key share of the signing key and the generator function;
• and
• outputting the second signing key share of the signing key to an entity based at least in part on verifying that the public key is equal to the summation and on verifying that the result of the execution of the zero-knowledge proof is valid.

A first device, comprising:

• one or more memories storing processor-executable code;
• and
• one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the first device to:
• execute, with a second device, a secure computation protocol that uses an input of a first decryption key share of a decryption key, a first signing key share of a signing key, and a ciphertext corresponding to an encryption of the signing key, wherein execution of the secure computation protocol results in output, to the second device, a second signing key share of the signing key;
• generate a first public key share of a public key based at least in part on the first signing key share of the signing key and a generator function;
• execute a zero-knowledge proof that the first device possesses the first signing key share of the signing key such that the first public key share of the public key corresponds to a product of the first signing key share of the signing key and the generator function;
• transmit information indicative of the first public key share of the public key and a result of execution of the zero-knowledge proof to the second device;
• and
• output the first signing key share of the signing key to an entity based at least in part on a verification by the second device involving the first public key share of the public key and the result of the execution of the zero-knowledge proof.