Quantum Computing, Cryptography, Computer Science.
own random number j She computes gʲ and (gᵏ)ʲ She keeps j and (gᵏ)ʲ secret. But she encrypts a message using (gᵏ)ʲ as the key. She sends the message and gʲ to Bob. Bob now has k, gʲ and the encrypted message. Bob then calculates (gʲ)ᵏ but this is the same as (gᵏ)ʲ so he can decrypt the message.