I generate an MD5 message digest fingerprint of the phrase: "2012 TR3 NAAEC CNA Supp" and it produces the string 80c55979acb8198c4445c25810e4e630. I update this for next year and change this message to: "2013 TR3 NAAEC CNA Supp" What will happen to the MD5 signature? Briefly explain your answer.
Try an answer before revealing the guidance below.
Key Concepts
- Cryptographic hash
- Fixed 128-bit output
- Avalanche effect
- Collision resistance
Answer Approach
- Note how small the change to the input is.
- Recall how a cryptographic hash reacts to small input changes.
- State what stays the same about the output (its length).
Full Answer
Answer status: Draft answer (unofficial). Revision notes, not an official marking scheme.
The MD5 digest will change completely: it will be a different, unpredictable 128-bit value (still 32 hex digits), with roughly half of its bits different, even though only one character of the input changed. A cryptographic hash is designed so that any change to the input produces an unrelated output (avalanche effect) and it is infeasible to find two messages with the same digest; this is what makes the digest useful for detecting changes.
Shortcuts: K concepts · A approach · F answer · R reviewed · B bookmark · ← / → previous / next