Final answer:
The real world key length for DES is 56-bits due to limitations imposed by the NSA to ensure the ability to break the encryption. Over time, advances in technology made it easier to crack a 56-bit key.
Step-by-step explanation:
The real world key length for DES (Data Encryption Standard) is only 56-bits due to a limitation imposed by the US National Security Agency (NSA) during the development of the encryption algorithm. The key length was intentionally reduced from the original 64-bits to make it weaker against brute force attacks. At the time, the NSA was concerned about the computational power available to potential adversaries and wanted to ensure that they could break the encryption if necessary.
By limiting the key length to 56-bits, the developers of DES compromised on its security. However, at the time of its creation in the 1970s, it was believed to be strong enough to withstand attacks. Over time, advancements in technology made it easier to launch brute force attacks on a 56-bit key, and in the late 1990s, the EFF (Electronic Frontier Foundation) demonstrated that the key could be cracked with sufficient computational power.
DES has since been replaced by more secure algorithms such as AES (Advanced Encryption Standard), which supports key lengths of 128, 192, and 256 bits, providing a much stronger level of security against brute force attacks..