Key Based Cipher Types

June 01, 2019 | 2 Minute Read

There are 2 broad types of key based Ciphers - Symmetric and Asymmetric Key based ciphers

Symmetric/Private Key based

• The same secret key is used for both encryption and decryption
• Fast and efficient, the only pre-requisite is that the secret keys have to be exchanged between both the parties in a secure way (Asymmetric Key Ciphers can help with key exchange).
• There are 2 types of symmetric key algorithms
  • Block Ciphers encrypt data in blocks of bytes, padding the plain text to make it a multiple of the block size. Typical block sizes are 8 or 16 bytes. E.g. DES, AES
  • Stream ciphers encrypt data as a sequence of bytes/digits, one byte/digit at a time. E.g. RC4, A5

Asymmetric/Public Key based (eg. RSA)

• There is a mathematically linked key pair(private key and public key) where one key cannot be derived from the other.
• Data encrypted using the public key can be decrypted only using the corresponding private key.
• Data encrypted using the private key can be decrypted only using the corresponding public key.
• The public key is distributed and accessible by everyone and the private key is a closely guarded secret.
• Key generation, encryption and decryption are more computing intensive than symmetric cryptography in general.
• The data size should be less than the key size in Assymetric key cryptography
• This is mostly used for establishing a symmetric key, for digital signatures and for non-repudiation.