code: function( signature, input, key ) {
  
      var length = ( this.bits / 8 | 0 ) + ( this.bits % 8 !== 0 ? 1 : 0 )
      if( signature.length !== length * 2 )
        return false
  
      var sig = ECDSASignature.encode({
        r: new BigNum( signature.slice( 0, length ), 10, 'be' ).iabs(),
        s: new BigNum( signature.slice( length ), 10, 'be' ).iabs(),
      }, 'der' )
  
      return crypto.createVerify( this.algorithm + this.bits )
        .update( input )
        .verify( key, sig, 'base64' )
  
    }
docs: Verify an ECDSA signature
  @internal used by `.verify()`
  @param  {Buffer} signature
  @param  {Buffer} input
  @param  {Buffer} key
  @return {Boolean}