This disclosure relates to blockchain-based transaction verification. Some aspects include receiving, by a blockchain system, transaction data to be verified. The transaction data includes plaintext transaction information and at least one piece of verifier signature data. The plaintext transaction information includes a designated-verifier information set that identifies verifiers that have been designated to verify the plaintext transaction information and that includes, for each of one or more verifiers, a piece of designated-verifier information. Each piece of signature data includes a digital signature generated by one of the verifiers. The blockchain system obtains an authenticated information set by verifying each digital signature. The authenticated information set includes the piece of designated-verifier information for each verifier for which the digital signature is successfully verified. The blockchain system determines that the transaction data is verified successfully when the authenticated information set includes a pre-determined quantity of pieces of designated-verifier information.