PPK is an index used to calculate process performance or process performance in SPC control chart.
CPK principle:
CPK key management system is a key generation and management system based on discrete logarithm problem, which constructs public key and private key matrix according to the mathematical principle of discrete logarithm problem.
Hash function and cryptographic transformation are used to map the entity's identity to the row coordinate and column coordinate sequence of the matrix, which is used to select and combine matrix elements and generate a large number of public key and private key pairs composed of public key and private key, thus realizing identity-based super-large-scale key production and distribution.