Then, after user Ua submits the blockchain transaction to the blockchain network, each blockchain node in the blockchain network can execute the blockchain transaction in the blockchain network after completing consensus processing on the blockchain transaction. Correspondingly, the account balance of each user recorded in the blockchain ledger changes accordingly. User Ua takes out the asset with value of m and receives the change amount in the blockchain transaction, and therefore asset c_a in the blockchain ledger is updated to [c_a?c(pk_0, m)+c_0(pk_0, m_0)] (if an addition/subtraction operation of plaintext data corresponds to a multiplication/division operation of homomorphic ciphertext, c_a is updated to [c_a÷c(pk_0, m)×c_0(pk_0, m_0)]). An additive homomorphism feature is satisfied because c_a, c(pk_0, m), and c_0(pk_0, m_0) are all generated by performing encryption by using public key pk_0 of user Ua. Therefore, a value obtained after user Ua decrypts [c_a?c(pk_0, m)+c_0(pk_0, m_0)] (or [c_a÷c(pk_0, m)×c_0(pk_0, m_0)]) by using corresponding private key sk_0 is equal to (m_a?m+m_0). Similarly, user Ub receives transfer amount 1 in the blockchain transaction, and therefore asset c_b in the blockchain ledger is updated to [c_b+c_1(pk_1, m_1) (if an addition/subtraction operation of plaintext data corresponds to a multiplication/division operation of homomorphic ciphertext, c_b is updated to [c_b×c_1(pk_1, m_1)]), and decryption can be performed by using private key sk_1, and an obtained value is equal to (m_b+m_1). User Uc receives transfer amount 2 in the blockchain transaction, and therefore asset c_c in the blockchain ledger is updated to [c_c+c_2(pk_2, m_2)] (if an addition/subtraction operation of plaintext data corresponds to a multiplication/division operation of homomorphic ciphertext, c_c is updated to [c_c×c_2(pk_2, m_2)]), and decryption can be performed by using private key sk_2, and an obtained value is equal to (m_c+m_2).