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Asymmetric-key algorithms are algorithms used in cryptography that use two different keys a public key for encryption and a private key for decryption. These keys are mathematically related, but the private key cannot be easily derived from the public key.

Types:

RSA (Rivest–Shamir–Adleman): It uses large prime numbers to generate the key pair and supports both encryption and digital signatures

DSA (Digital Signature Algorithm): DSA is primarily used for creating digital signatures, ensuring the authenticity.


Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both encryption of plaintext and decryption of ciphertext 

Types:

Stream Cipher: Stream Cipher Converts the plain text into cipher text by taking 1 byte of plain text at a time.

Block cipher: Converts the plain text into cipher text by taking plain text's block at a time

DES?

DES stands for Data Encryption Standard. It is a symmetric-key algorithm used to encrypt and decrypt data to keep it safe and private. DES uses the same key for both encryption and decryption. It was developed by IBM and adopted by the U.S. government in the 1970s.

DES uses a 56-bit key to convert plaintext (normal data) into ciphertext (coded data) through a process called encryption. The data is divided into 64-bit blocks, and each block goes through 16 rounds of operations, including permutations, substitutions, and XOR operations.

The main purpose of DES is to protect information from being read by unauthorized people. 

DES function?

The DES function is the core part of the DES encryption process. It takes 32 bits of data (the right half of the block) and mixes it with a 48-bit round key to produce a new 32-bit output. This process is repeated in each of the 16 rounds of DES.

The DES function has four main steps:

  1. Expansion – The 32-bit input is expanded to 48 bits.

  2. XOR with Key – The 48-bit expanded data is XORed with a 48-bit round key.

  3. Substitution (S-boxes) – The result is divided into eight 6-bit parts and passed through 8 S-boxes. Each S-box gives a 4-bit output, resulting in 32 bits.

  4. Permutation (P-box) – The 32-bit output from S-boxes is permuted (rearranged) to increase diffusion.

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