Engineering Sandbox lab ยท blockchain systems

Edit a block, watch the chain break, then mine it back into coherence.

This lab is best when you treat the chain like a live dependency graph. Change the earliest payload, watch downstream hashes and validity states fall out of sync, then repair the first block so you can see why one successful mine is not enough to fix the whole system.

Tamper with block dataRead the hash cascadeMine to repair one link at a time
Try this first

Edit the data in block 1, look at block 2's previous-hash field, then press Mine on the first block only. The fastest way to understand the chain is to watch which state repairs and which state stays broken.

Start at block 1Open distributed view

What to observe

  • 1
    Tamper early. Change the first block so the rest of the chain has to react to it.
  • 2
    Track propagation. Compare the current hash with the next block's previous-hash field.
  • 3
    Repair locally. Mine the edited block and notice that downstream blocks still need work.

Why this matters

The point of the demo is not just to produce a valid-looking hash. It is to see how immutability emerges from linked dependencies: one edit changes one hash, which invalidates every later reference that trusted it.

Read the states

  • 1
    Green blocks are locally valid again after mining.
  • 2
    Red blocks still trust an older previous hash and need their own repair step.
  • 3
    Scroll right to keep following the cascade into later blocks.

Keep going

The row is horizontally scrollable because the later blocks matter. Use the distributed view when you want to compare competing peers, or jump into keys and signatures once the chain state feels concrete.

Open distributed viewOpen keys and signatures

Blockchain

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