Provided is a computer implemented method of providing a blockchain based traceability service. The method comprises, for each secret from a set of secrets associated with respective ones of a set of parameters for a traceable item, generating a proof to provide a set of proofs. The method includes generating a ciphertext based on a public data encryption key from a set of public data encryption keys associated with said parameters for the traceable item, and information of said traceable item. The preceding step is repeated for each pair of identifier and public data encryption key. The method involves uploading to the blockchain the generated ciphertext, the respective identifier, a hash value of the respective secret, and the respective proof for each parameter of the traceable item, verifying in the blockchain the set of uploaded proofs, and storing verified data in the blockchain.