docs: function( digest ) {
  
      var signature = ECDSASignature.decode( digest, 'der' )
      var length = ( this.bits / 8 | 0 ) + ( this.bits % 8 !== 0 ? 1 : 0 )
  
      var r = Buffer.from( signature.r.toString( 'hex', length ), 'hex' )
      var s = Buffer.from( signature.s.toString( 'hex', length ), 'hex' )
  
      return Buffer.concat([ r, s ], r.length + s.length )
  
    }