Cryptography and Network Security. Cryptography is the art, science and study of secure communication. Network security is the protection of networks.
Cryptography is the art, science and study of secure communication and it uses mathematics, computer science, and information theory.
Network security is the protection of computer networks against unauthorized access. It is performed by implementing a combination of policies, physical measures and active systems. Further, to prevent harm or unwanted access to information.
Information security is the practice of controlling access to stored information. In order to protect it from unauthorized use and disclosure.
What can Cryptography do?
Cryptography transforms plaintext into ciphertext. In order to make messages unreadable by anyone except those possessing special knowledge, usually referred to as a key. This transformation is not reversible without the key for decrypting the ciphertext back into plaintext. Cryptography is used for securing information in an information system and for ensuring its authenticity, integrity, non-repudiation, and confidentiality.
Cryptography can be categorized into two main categories: symmetric cryptography (or private-key cryptography) and asymmetric cryptography (or public-key cryptography). Symmetric cryptography uses one key that both sender and receiver share in order to encrypt and decrypt the data. While asymmetric cryptography uses a pair of keys called a public key and a private key.
A public key and private key
The public key can be free to anyone. While the private key must be secret by its owner at all times. As anyone who has access to this key will be able to decrypt any data that has been encrypted using the corresponding public key.
The private key must also be kept highly secure. Since anyone with access to it will be able to decrypt data encrypted using the corresponding public key. In this scenario, a private-key cryptography system would be more suitable. Since only one key would need to be shared. While a public-key cryptography system would require that both parties have access to both keys. Further, may result in sharing more information than the intended or desirable between parties communicating over an insecure channel.
Symmetric/ asymmetric cryptography
Symmetric cryptography provides confidentiality by hiding the message. So that only authorized recipients can read it. Asymmetric encryption provides authentication by proving that a message comes from someone who holds the matching private key. And ensures non-repudiation so that sender cannot deny sending a message.
Advantage and disadvantages
The biggest advantage of asymmetric cryptography is that the public key can be freely and openly distributed to anyone while keeping private key highly secure making it difficult to use it fraudulently.
A disadvantage of public-key cryptography system is that if a method for efficiently factoring large composite numbers into primes is discovered, then the private key of a public-key cryptosystem could potentially be calculated using this method and the system would no longer be secure.
Symmetric cryptography is usually preferred in situations where control over the shared secret keys must be maintained by both parties and when their communication channel cannot be trusted or they are unable to rely on a third-party certifiers.
An example, of when symmetric cryptography is used, would be a financial institution protecting information about your bank accounts from unauthorized access. Since both parties already share the secret keys, all that is needed is for them to agree on a shared secret key for encryption and decryption.
Public-key encryption may be used in situations where sharing of the cryptographic key is not possible or desirable but the ability to verify digital signatures is required.