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Tips on using Pointy Castle

Use correct typing

The package makes great use of abstract classes, inheritance and generic types.

Sometimes a method will return an abstract class that needs to be cast into its actual type before it can be properly used.

final pair = keyGen.generateKeyPair(); // returns AsymmetricKeyPair<PublicKey, PrivateKey>

final pub = pair.publicKey; // PublicKey - not very useful
final pvt = pair.privateKey; // PrivateKey - not very useful

final rsaPub = pair.publicKey as RSAPublicKey;
final rsaPvt = pair.privateKey as RSAPrivateKey;

At other times, a generic typed parameter needs to be of a specific subtype for the method to work (even though the type system accepts the base generic type). Make the generic type more specific for the subclass that is being used.

RSAPrivateKey pvtKey = ... // RSAPrivateKey implements PrivateKey
RSASigner signer = ...

// PrivateKeyParameter is defined as:
//
// class PrivateKeyParameter<T extends PrivateKey>
//     extends AsymmetricKeyParameter<T> {
//   PrivateKeyParameter(PrivateKey key) : super(key);
// }

// This is type correct, but won't work:

signer.init(true, PrivateKeyParameter(pvtKey)); // incorrect: fails at runtime

// This works:

signer.init(true, PrivateKeyParameter<RSAPrivateKey>(pvtKey)); // correct

Algorithm name property

Every implementation classes have an algorithmName property.

If you have created an object and want to find out the name to use with the registry, print out its algorithmName.

How do you find the class to create? A recursive grep over the source code can be very useful.

Navigating the API reference

The Pointy Castle API reference can be difficult to navigate. Each implementation class is in a separate library to improve the performance of loading (when used without the registry) and the library names are long.

Try looking in the one of the combined libraries for classes: