The Data Encryption Standard (DES) is a symmetric encryption algorithm which uses the same key to both encrypt and decrypt data. It does this by encrypting a block of 64-bits in size using a 56-bit key. The size of the key makes a difference in the strength of the encryption itself; in this case, a 56-bit key is used per block. The smaller the key, the weaker and more vulnerable the encryption/algorithm is to being deciphered by a hacker.