Cryptography categorized based on number of keys used for encryption and decryption; Below are list of cryptography catgories 

1. Secret Key Cryptography – It is also call symmetric encryption where for both encryption and decryption uses same key. This is mainly used for confidentiality.
2. Public Key Cryptography – It is also called asymmetric encryption; this algorithm uses two key’s one for encryption and one for decryption. mainly used for authentication.
3. Hash Function – It uses to convert to text in such way that the input cannot be recoverable by using mathematical function.