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Encryption scheme #30

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Encryption scheme #30

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LukePearson1
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@LukePearson1 LukePearson1 commented Aug 11, 2020 •
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This PR is the implementation of the out of circuit (standard), ElGamal Encryption scheme using the JubJub Elliptic curve
group.

This closes #28.

Luke Pearson added 3 commits August 11, 2020 11:09
Add Elgamal to lib.rs
c1b04b5 
This commit adds elgamal to the
lib.rs
Add Elgamal module
689e0b5 
The elgamal encryption scheme is
needed as an encryption method
across several libraries, which
import jubjub. This commit adds
them in.
Remove std code
35e9589 
The standard code was preventing
the tests from producing the correct
errors. This is removed in this commit.
@LukePearson1 LukePearson1 added bug area:cryptography anything related to cryptographic primitives, hashing and ZKP labels Aug 11, 2020
@LukePearson1 LukePearson1 self-assigned this Aug 11, 2020
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LukePearson1 commented Aug 11, 2020 •
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The tests on this PR fail. With a result as follows:

thread 'elgamal::test_encryption' panicked at 'assertion failed: (left == right)
left: Message([17, 173, 29, 111, 166, 181, 34, 52, 147, 76, 48, 146, 54, 198, 170, 2, 24, 178, 120, 22, 117, 105, 110, 105, 65, 234, 66, 232, 8, 189, 252, 8]),
right: Message([98, 11, 123, 123, 1, 71, 136, 171, 251, 67, 119, 122, 186, 185, 142, 75, 68, 254, 120, 246, 246, 168, 103, 164, 6, 56, 29, 84, 212, 174, 249, 21])
`

The left is the message going in and the right is the messaging coming out. After encryption and decryption, this is not the same message.

My assumption is the decrypt is failing as the decrypt function uses the curve order and SecretKey to compute the inverse mod via lagrange theorem.
This is done as an 'alternative' as there is no inverse mod or power mod functions.

A suggested fix is to implement these functions, either by extended Euclidean Algorithm, or the Savas and Koc in Zerocaf.
@vlopes11 @CPerezz

Add power and inverse mod functions
e3cdd22 
Inline with the comments on the PR
linked to this issue. The encrypt
and decrypt functions should rely
upon the exponentiations and inverse
modular operations. These have been
added in this commit.
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#32 covers this issue so the PR can be closed.

@CPerezz CPerezz deleted the encryption_scheme branch April 12, 2021 09:40
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Implement ElGamal encryption schema
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