Linked Paintings

A blockchain metaphor

Alice is a painter who uses a camera to capture her canvas masterpiece, then affixes the printed photograph to the top left corner of a blank canvas and begins to paint, repeating this process for every painting.

Alice is able to tell which of two paintings is older by glancing at its photograph to see its place in history.

If a malicious attacker, Mallory, wants to modify a painting she would need to re-take the photograph and re-affix it to the following canvas, but now that canvas is modified and so Mallory would need to repeat the process for all following paintings.

The photographs link the paintings together and if instead of paint it was your data then the blockchain would link your data together using a hash function in place of a camera. If Mallory tries to modify your data in a block the hash function would return a different hash, and so the next block would need to be modified to reference the previous' new hash, but now that block is modified and so Mallory would need to repeat the process for all following blocks.