code: function( signature, input, key ) {
  
      var verifier = crypto.createVerify( this.algorithm + this.bits )
  
      return verifier.update( input )
        .verify( key, signature )
  
    }
docs: Verify an RSA signature
  @internal used by `.verify()`
  @param  {Buffer} signature
  @param  {Buffer} input
  @param  {Buffer} key
  @return {Boolean}