Techniques are disclosed relating to generation of cryptographic private keys. In some embodiments, a computing system receives a request for a private key for use with a service that uses a key of a first length, where the request specifies a key of a second length that is less than the first length. The system then generates a hashing scheme based on the second length and a key computation time, where the hashing scheme includes a number of hashing rounds and a set of hashing functions. The system creates a synthetic key of the second length and uses the synthetic key and the hashing scheme to create a normal key of the first length, where the synthetic key permits a user to access the service by supplying the synthetic key and without having to supply the normal key. The disclosed cryptographic techniques may advantageously allow for memorization of private keys.