Encryption 

Symmetric encryption/ Private key model \n Requirements

• A Private key

• Three algorithms

  • A random Private key generator algorithm that generates a random key of a specified length (L): KeyGen(L) -> K

  • An encryption algorithm that takes the Private key (K) and the plaintext (M) and then returns a ciphertext (C): Enc(K, M) -> C

  • A decryption algorithm that takes the Private key (K) and the ciphertext (C) and then returns the original plaintext (M): Dec(K, C) -> M

    

\n Asymmetric encryption / Public key model \n Requirements

• A Private key and a Public key
• Four algorithms
  • A random Private key generator algorithm that generates a random key of a specified length (L): KeyGen(L) -> Kₚᵣᵢᵥ
  • A random Public key generator algorithm that generates a random key of a specified length (L): KeyGen(L) -> Kₚᵤb
  • An encryption algorithm that takes the receiver's public key (Kₚᵤb) and the sender's plaintext (M) and then returns a ciphertext (C): Enc(Kₚᵤb, M) -> C
  • A decryption algorithm that takes the receiver's private key (Kₚᵣᵢᵥ) and the ciphertext (C) and then returns the original plaintext (M): Dec(Kₚᵣᵢᵥ, C) -> M

Good:

• key management is much simpler
• Alleviates the need to share secrets before communicating between parties

Bad:

• Much slower than Symmetric cryptography