Algorithm - A rule or procedure for solving a logical or mathematical problem.
Ciphertext - The encrypted version of a message, which may be decrypted only by someone who has the correct key.
Cryptography - The art of protecting information by encrypting it into an unreadable format. A secret key is used to decrypt the message into plaintext.
Decryption - The process of converting encrypted data back into its original form, so it can be understood.
Eve/Eavesdropper - A secret listener to private conversations.
Encryption - Encryption is the conversion of data into a form, called a ciphertext, that cannot be easily understood by unauthorized persons.
One-time pad - The only known form of encryption that is unbreakable. It relies on a random key that is used only once.
Photons - Discrete units of energy that make up light waves.
Plaintext - An original message before it is encrypted.
Quantum computer - A computer that exploits the quantum mechanical nature of particles to manipulate information as quantum bits, or qubits. It is many times more powerful than a conventional computer.
Quantum cryptography - An unbreakable form of cryptography that exploits quantum theory – in particular the uncertainty principle – which states that it is impossible to measure all aspects of an object with absolute certainty. Quantum cryptography guarantees the absolute secure exchange of a random series of bits, which is then used as the basis for a one-time pad key.
Quantum physics - The science that applies quantum laws at the atomic level.
RSA - The first system that fitted the requirements of public-key cryptography. It was invented by Ron Rivest, Adi Shamir and Leonard Adleman in 1977.