Future Business Leaders of America (FBLA) Cybersecurity Practice Test

What key strength does Triple DES effectively utilize according to experts?

1. 56 bits

2. 112 bits

3. 168 bits

4. 256 bits

The correct answer is: 112 bits

Triple DES, also known as 3DES, is a symmetric key block cipher that applies the Data Encryption Standard (DES) encryption algorithm three times to each data block. The key strength associated with Triple DES is particularly significant because it effectively uses multiple keys to enhance security. The effective key length of Triple DES is typically referred to as 168 bits, but it can actually be perceived as either 112 bits or 168 bits, depending on how the keys are structured. When using three 56-bit DES keys (since DES operates with a 56-bit key), the total key length can sum up to 168 bits. However, due to the nature of encrypting the data three times and the potential for key reduction through certain attacks, many experts consider the effective security strength to be 112 bits. So while Triple DES utilizes the aggregate of three 56-bit keys, the practical security strength it provides is often categorized as 112 bits, making it a significant enhancement over single DES, which only has 56 bits of effective strength. This dual perspective on key strength underlines why 112 bits is recognized as a critical measure of security in many expert analyses surrounding Triple DES.