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https://github.com/str4d/ed25519-java

Pure Java implementation of EdDSA
https://github.com/str4d/ed25519-java

crypto-library ed25519 eddsa java

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Pure Java implementation of EdDSA

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README 

        
EdDSA-Java

==========



[![Build Status](https://travis-ci.org/str4d/ed25519-java.svg?branch=master)](https://travis-ci.org/str4d/ed25519-java)



This is an implementation of EdDSA in Java. Structurally, it is based on the ref10 implementation in SUPERCOP

(see https://ed25519.cr.yp.to/software.html).



There are two internal implementations:

- A port of the radix-2^51 operations in ref10 - fast and constant-time, but only useful for Ed25519.

- A generic version using BigIntegers for calculation - a bit slower and not constant-time, but compatible

  with any EdDSA parameter specification.



To use

------



Download the latest .jar from the releases tab and place it in your classpath.



Gradle users:



```

compile 'net.i2p.crypto:eddsa:0.3.0'

```



Java 7 and above are supported.



The JUnit4 tests require the Hamcrest library `hamcrest-all.jar`.



This code is released to the public domain and can be used for any purpose. See `LICENSE.txt` for details.



Disclaimer

----------



There are **no** guarantees that this is secure for all cases, and users should

review the code themselves before depending on it. PRs that fix bugs or improve

reviewability are very welcome. Additionally:



- The unit test suite includes tests against

  [the data from the original Python implementation](https://ed25519.cr.yp.to/python/sign.input).

- The code (as of 97cea3f0d910fc627c7b57b1bc4d783cdd0c2a4a) was reviewed by

  [an independent developer](https://github.com/BloodyRookie).

- The code (as of dc9f58f2c874463c15465326efc040d17a627b3a) was audited by an independent third party,

  and the one issue found [was fixed](https://github.com/str4d/ed25519-java/pull/31).



Code comparison

---------------



For ease of following, here are the main methods in ref10 and their equivalents in this codebase:



| EdDSA Operation | ref10 function | Java function |

| --------------- | -------------- | ------------- |

| Generate keypair | `crypto_sign_keypair` | `EdDSAPrivateKeySpec` constructor |

| Sign message | `crypto_sign` | `EdDSAEngine.engineSign` |

| Verify signature | `crypto_sign_open` | `EdDSAEngine.engineVerify` |



| EdDSA point arithmetic | ref10 function | Java function |

| ---------------------- | -------------- | ------------- |

| `R = b * B` | `ge_scalarmult_base` | `GroupElement.scalarMultiply` |

| `R = a*A + b*B` | `ge_double_scalarmult_vartime` | `GroupElement.doubleScalarMultiplyVariableTime` |

| `R = 2 * P` | `ge_p2_dbl` | `GroupElement.dbl` |

| `R = P + Q` | `ge_madd`, `ge_add` | `GroupElement.madd`, `GroupElement.add` |

| `R = P - Q` | `ge_msub`, `ge_sub` | `GroupElement.msub`, `GroupElement.sub` |



Important changes

-----------------



### 0.3.0



- The library has been extensively profiled for contention issues in a multi-threaded environment.  The only

  remaining potential contention is in `EdDSANamedCurveTable.defineCurve()`, which will be rarely called.

- The public constant for the curve name has returned as `ED_25519`, and the curve specification has a public

  constant `ED_25519_CURVE_SPEC` to avoid repeated lookups when converting to and from encoded form for the

  public or private keys.

- `GroupElement` is now completely immutable, and all fields final, to avoid the need for `synchronized`

  blocks over mutable fields. This required some new constructors and paths to construction.

- `EdDSAPublicKeySpec.getNegativeA()` and `EdDSAPublicKey.getNegativeA()` now evaluate lazily, taking

  advantage of the immutability of `GroupElement.negate()`. This boosts the performance of the public key

  constructor when the key is just being passed around rather than used.

- Support for X509Key wrapped EdDSA public keys.



### 0.2.0



- Ed25519 is now named `Ed25519` in `EdDSANamedCurveTable`, and the previous public constant (containing the

  older inaccurate name) has been removed.



Credits

-------



- The Ed25519 class was originally ported by k3d3 from

  [the Python Ed25519 reference implementation](https://ed25519.cr.yp.to/python/ed25519.py).

- Useful comments and tweaks were found in

  [the GNUnet implementation of Ed25519](https://gnunet.org/svn/gnunet-java/src/main/java/org/gnunet/util/crypto/)

  (based on k3d3's class).

- [BloodyRookie](https://github.com/BloodyRookie) reviewed the code, adding many useful comments, unit tests

  and literature.