Basic Cryptographic Operation

Basic Cryptographic Operation

In this post, We will learn some terminologies that used in computer security.

Basic Terms in Cryptography

• Encryption: Encryption is a process to translate a plaintext to a cipher.
• Decryption: Decryption is a process to translate a cipher to plaintext as it was before encryption.
• Plaintext: This is a message, a string that we want send securely like an email, a text message etc.
• Cipher: Cipher is a secure message that produces as a result of encryption.
• Initialization vector (IV): IV provides semantic security to the cipher. It means that same message should have a different cipher.
• Padding: Padding is a way to take data that may or may not be a multiple of the block size for a cipher and extend it out so that it is. Padding required of may many cipher mode because data to be encrypted to the exact multiple of block size.
• Key: In cryptography, a key is a value that is applied using an algorithm to a string or block of unencrypted plaintext to produce encrypted text, or to decrypt encrypted text. There are two type of key
• Public Key: The public keys are shared over the network. it uses to encrypt plain text.
• Private Key: The private keys are stored securely and only respective know his private key. A key encrypted by the public key is decrypted by the private key

• Mode: Direct use of cipher is not advisable because an enemy can build a codebook equivalent to plaintext or ciphertext. There are five standard modes of operation.
• Electronic Code Book (ECB)
• Cipher Block Chaining (CBC)
• Cipher Feedback  (CFB)
• Output Feedback (OFB)
• Counter (CTR) 

Cryptography Model

• There are two type of encryption and decryption models that widely used in the security domain to secure sensitive information
• Symmetric Key Model
• Asymmetric Key Model

Symmetric Key Model

In symmetric key encryption, we use the same key to encrypt as well as decrypt.

Above image representing an example of symmetric encryption. You can clearly see all those in some scenarios a hacker able to get cipher but he/she can not read data because he does not have the key. But there is a problem here because both parties are using same how do they share this key? We use key wrapping and unwrapping technique to protect key.

Key Wrapping and Unwrapping

• Key Wrapping: Key wrapping is a technique to encrypt a symmetric key material. It is used to protect keys at rest or transmit them over insecure networks
• Key Unwrapping: Key unwrapping is a technique used to decrypt a key material.

Asymmetric Key Model

 Asymmetric cryptographic systems use one key to encrypt data and the different key to decrypt. These keys are known as public and private key

In the asymmetric algorithm, the public key of the recipient is share across the channel. The sender encrypts the message with the public key of recipient and recipient decrypt with his private key which is securely stored.

Symmetric Key Algorithms 

There is a set of the symmetric key algorithm which use to encrypt a plaintext. We will discuss some of them here

1. Advanced Encryption Standard (AES)
2. Data Encryption Standard (DES)
3. Triple Data Encryption Algorithm (3DES)

Asymmetric Key Algorithms

There is a set of an asymmetric key algorithm which use to encrypt a plaintext. We will discuss some of them here

1.  Rivest Shamir Adleman (RSA)

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