Blockchain encryption techniques are provided. An exemplary method includes sending a signed transaction with at least two users to a blockchain; obtaining, by a first user, a public key of a second user from the blockchain; generating, by the first user, a symmetric key by combining a private key of the first user and the public key of the second user; encrypting, by the first user, a data item using the symmetric key; and providing the encrypted data item to the blockchain. The second user obtains the encrypted data item and a public key of the first user from the blockchain, and decrypts the encrypted data item using the symmetric key generated, by the second user, by combining a private key of the second user and the public key of the first user.