code: function (data, scheme) {
        scheme = scheme || SCHEME;
        return this._key.decrypt(forge.util.decode64(data), scheme);
      }
docs: Decrypt RSA encrypted data
  @param {String} data The data to decrypt
  @param {String} [scheme='RSA-OAEP'] The mode to use in decryption. 'RSA-OAEP', 'RSAES-PKCS1-V1_5' are allowed schemes.
  @return {String} The decrypted data