Future Business Leaders of America (FBLA) Cybersecurity Practice Test

What is the effective key length of DES used in encryption?

1. 64 bits

2. 56 bits

3. 48 bits

4. 32 bits

The correct answer is: 56 bits

The effective key length of the Data Encryption Standard (DES) used in encryption is 56 bits. DES employs a 64-bit key; however, only 56 bits of that key are actually used in the encryption process. The remaining 8 bits are utilized for parity checks, meaning they serve a purpose in error detection rather than providing additional security. This effective key size of 56 bits has been a point of concern because it is relatively short by modern encryption standards, making DES susceptible to brute-force attacks, where an attacker attempts every possible key combination. As computing power has increased, it has become increasingly feasible for attackers to crack DES encryption in a reasonable time frame. Hence, while the key input is technically 64 bits, the practical strength of the encryption provided by DES is determined by the 56 bits that are effectively utilized for the encryption process.