Which of the following statements about 56-bit key size is true according to the material?

• A. It is sufficient for major business transactions
• B. It is sufficient for most residential consumer applications
• C. It is considered a strong length
• D. All of the above

Answer: (B)

The key idea here is how key length relates to the level of security it provides. A 56-bit key comes from DES-era cryptography and is relatively short by today’s standards. In the material’s context, this length is described as sufficient for typical residential, non-critical use where the threat model assumes limited attacker resources. It isn’t considered a strong length, meaning it wouldn’t be trusted for protecting major business transactions or highly sensitive data against capable adversaries. So, describing 56-bit keys as adequate for most residential consumer applications matches that assessment, while recognizing they would not be adequate for high-security needs. In modern practice, longer keys (128-bit or more) are preferred for stronger protection.