US Patent 10594487 Password management and verification with a blockchain

An example operation may include one or more of determining whether one or more password strings are related to a password, the password strings are transmitted from a user device, hashing the one or more password strings to create one or more password hash values, determining whether the one or more password hash values match any internal password hash values of an internal password history chain stored in an internal blockchain, determining whether the one or more password hash values match any external password hash values of an external password history chain stored in an external blockchain, and responsive to determining the one or more password hash values do not match any internal password hash value and any external password hash values, storing a new password in one or more of the internal blockchain and the external blockchain.