Cryptography is the science encompassing the principles(rules) and methods converting an intelligible message into one that is unintelligible, and then reconverting that message back to its original form.
Various terms that are important to be noted:
The original intelligible message.
The transformed message.
Some critical information used by the cipher, known only to the sender & receiver
Cryptography can be discussed with following techniques
Encryption is the conversion of data into a form, called a cipher text, that cannot be easily understood by unauthorized people.
Decryption is the process of converting encrypted data back into its original form, so it can be understood.
There are two types of encryption:
1. Symmetric (private) key, and
2. Asymmetric (public) key encryption.
Symmetric Key Encryption
Symmetric key, also referred to as private key or secret key, is based on a single key and algorithm being shared between the parties who are exchanging encrypted.
The same private key both encrypts and decrypts message
- If the key is larger, the more secure the scheme Symmetric key encryption is fast.
- The system key or algorithm has to be shared.
- Private key cryptosystems are not well suited for spontaneous communication over an unsecured network.
- Symmetric key provide no process for authentication or non-repudiation.
Asymmetric Key Encryption
- The Asymmetric cryptosystem is also known as public key cryptography.
- Public key cryptography used two key as opposed to one key for a symmetric system.
- There is a public key and a private key.
- Each user has a private key that decrypted only the message that were encrypted by its public key.
- The private key is kept secret.
- All public keys are published in a directory.
- Asymmetric or public key cryptography is more versatile.
- A Public key allows for secure spontaneous communication over an open network, it is more scalable for large system.
- No secret sharing necessary
- Authentication supported
- Provides non-repudiation
- Slower or computationally intensive
- Certificate authority required