69 lines
1.6 KiB
Markdown
69 lines
1.6 KiB
Markdown
# Diffie-Hellman
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Diffie-Hellman key exchange.
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Alice and Bob use Diffie-Hellman key exchange to share secrets. They
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start with prime numbers, pick private keys, generate and share public
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keys, and then generate a shared secret key.
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## Step 0
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The test program supplies prime numbers p and g.
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## Step 1
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Alice picks a private key, a, greater than 1 and less than p. Bob does
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the same to pick a private key b.
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## Step 2
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Alice calculates a public key A.
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A = g**a mod p
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Using the same p and g, Bob similarly calculates a public key B from his
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private key b.
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## Step 3
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Alice and Bob exchange public keys. Alice calculates secret key s.
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s = B**a mod p
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Bob calculates
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s = A**b mod p
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The calculations produce the same result! Alice and Bob now share
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secret s.
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## Setup
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Go through the setup instructions for Kotlin to install the necessary
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dependencies:
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[https://exercism.io/tracks/kotlin/installation](https://exercism.io/tracks/kotlin/installation)
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## Making the test suite pass
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Execute the tests with:
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```bash
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$ gradlew test
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```
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> Use `gradlew.bat` if you're on Windows
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In the test suites all tests but the first have been skipped.
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Once you get a test passing, you can enable the next one by removing the
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`@Ignore` annotation.
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## Source
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Wikipedia, 1024 bit key from www.cryptopp.com/wiki. [http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange](http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have
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completed the exercise.
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