Private Key cryptography is also known as ______ cryptography.

Cryptographic systems are classified by how many keys they use and how those keys are shared. When a single key is shared secretly between the sender and receiver and used for BOTH encryption and decryption, the scheme is called Symmetric-key cryptography -- and standard cryptography texts (e.g. Kahate's Cryptography and Network Security, and introductory university crypto courses) also name this same category Secret-key cryptography or Private-key cryptography, in contrast with Public-key cryptography for asymmetric schemes.

The stem's blank asks for the alternate name of 'Private Key cryptography.' Since 'private-key cryptography' is the established synonym for the single-shared-secret-key model, the blank is filled by Symmetric -- the same secret key encrypts and decrypts the data on both ends.

• The identical key is used for both encryption and decryption.

• It is computationally faster and more efficient than asymmetric cryptography.

• It requires the key to be shared securely between sender and receiver beforehand -- the key-distribution problem.

• It is the preferred choice where speed matters, such as bulk data encryption over a network.

Contrast this with Asymmetric cryptography, which uses a mathematically linked PAIR of keys -- a public key that can be shared openly, and a private key kept secret by its owner; data encrypted with one key can only be decrypted with the other. Because a 'private key' also exists inside this pair, it is easy to assume 'private-key cryptography' must mean the asymmetric scheme -- but as a name for an entire cryptographic CATEGORY, 'private-key cryptography' denotes the shared-secret-key model above; the asymmetric category itself is properly named Public-key cryptography, never 'private-key cryptography.'