Examples of popular symmetric cyphers include Twofish , Serpent , AES ( aka Rijndael ) , Blowfish , CAST5 , RC4 , TDES , and IDEA . Some examples of popular and well-respected symmetric algorithms include Twofish , Serpent , AES ( Rijndael ) , Blowfish , CAST5 , RC4 , 3DES , and IDEA .