Foundations & Encodings Checkpoint

Trace exact representations and state, diagnose a failure, and return to its specific explanation.

Get every question correct to pass this checkpoint. You can review feedback, revise your answers, and submit again.

1. CompactSize encodes 65536 using how many total bytes? Enter a decimal integer.

2. A decoder sees fd fc 00. What should canonical CompactSize decoding do?

Select one answer.

Reject the complete but nonminimal representation Accept 252 with three bytes consumed Treat fc as a signed negative integer Wait for a fourth byte

3. Decode fd 2c 01 99 as one CompactSize field. How many bytes are consumed? Enter a decimal integer.

4. For fe ff ff 00 00, why does decoding fail?

Select one answer.

The value needs nine bytes The bytes encode 65535, which requires the shorter fd branch Little-endian integers cannot end in zero The prefix fe is not supported

5. Base58-only bytes 00 00 3a represent integer 58. Its ordinary Base58 digits are 21. What preserves the original bytes?

Select one answer.

Return 21 Return 0021 Append 11 after 21 Prefix two alphabet-zero characters, giving 1121

6. An attacker changes a payload and computes a matching Base58Check checksum. What does successful decoding establish?

Select one answer.

The sender owns its private key The original payload was unchanged The supplied body matches its unkeyed checksum The contents are encrypted

7. Your codec round-trips its own values but disagrees with the published vector. What is the best next check?

Select one answer.

Remove the checksum Compare alphabet, digit direction, zero handling, and raw-byte hashing against an explicit vector Assume the external vector is wrong Increase the checksum length

8. A decoded Base58 string contains four bytes total. Can it be a valid Base58Check result for this API?

Select one answer.

Yes, if all bytes are zero Yes, because an empty payload has no version No: even an empty payload needs one version byte and four checksum bytes No: every payload must contain exactly 20 bytes

Auto-advance on pass

Join Discord