JCEd25519 is a JavaCard implementation of Ed25519 signing using public JavaCard API.

The implementation uses (modified) JCMathLib library to perform necessary operations like EC and BigInt arithmetic. And in case SHA512 is not supported by given JavaCard, its software re-implementation is used.

Structure of this repository is based on JavaCard Gradle Template.

• Clone this repository

git clone --recursive https://github.com/dufkan/JCEd25519

• Select your JavaCard in JCEd25519.java file

• Build the applet

./gradlew buildJavaCard  --info --rerun-tasks

• Send initialize APDU 00DF000000 to the card. For example, using GlobalPlatform Pro

gp --apdu 00A404000C6A6365643235353139617070 --apdu 00DF000000 -d

The optimizations in the implementation require the nonce to be generated randomly to be secure; otherwise, the implementation could be made to reuse nonce for signing of a different challenge. This is a minor deviation from Ed25519 specification, but it cannot be externally observed, unless multiple signatures of the same data are issued.

The implementation was tested on J3R180, J2E145G.