@AccessesPartialKey
  private static EcdsaPrivateKey toEcdsaPrivateKey(
      com.google.crypto.tink.jwt.JwtEcdsaPrivateKey privateKey) throws GeneralSecurityException {
    return EcdsaPrivateKey.builder()
        .setPublicKey(JwtEcdsaVerifyKeyManager.toEcdsaPublicKey(privateKey.getPublicKey()))
        .setPrivateValue(privateKey.getPrivateValue())
        .build();
  }
This key manager generates new {@code JwtEcdsaSignKey} keys and produces new instances of {@code
JwtPublicKeySign}.
java_src/src/main/java/com/google/crypto/tink/jwt/JwtEcdsaSignKeyManager.java