Channels ▼


Trust Me, I Won


1. You take 81 cards and write 1 on nine of them, 2 on nine of them,3 on nine of them,..., 9 on nine of them. Then you lay out the cards of the initial board configuration face up (so the number is in evidence).Then you think. Then you find your solution and put the other cards face down.

Now when the Verifier comes, you offer any row, any column, or any 3x3 Sudoku box. The verifier points to one or the other. You take those 9 cards make them all face down and shuffle them. After you have shuffled them sufficiently, you demonstrate to the Verifier that you have all numbers between 1 and 9.

2. You send me out of the room and you take a few grains, say some number between 1 and 30, after covering the bucket with a cape. You call me back in. If I know how many you've removed, then I'm either very lucky or I may have the ability I claim. If you try this test 100 times, then you might be convinced.

The problem of the sand counter can be solved by most kids 10 or older. If you wish, try it out on a kid you know. The Sudoku zero knowledge proof was developed by Professor Michael Rabin.

Reading: The origin of zero-knowledge proofs comes from a now-classic paper by Shafi Goldwasser, Silvio Micali, and Charles Racoff. The paper was rejected several times before it first appeared. What do program committees know?

Related Reading

More Insights

Currently we allow the following HTML tags in comments:

Single tags

These tags can be used alone and don't need an ending tag.

<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags

These require an ending tag - e.g. <i>italic text</i>

<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

Dr. Dobb's encourages readers to engage in spirited, healthy debate, including taking us to task. However, Dr. Dobb's moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing or spam. Dr. Dobb's further reserves the right to disable the profile of any commenter participating in said activities.

Disqus Tips To upload an avatar photo, first complete your Disqus profile. | View the list of supported HTML tags you can use to style comments. | Please read our commenting policy.