code: function Signature(req, buf) {
    this.req = req;
    this.rawBody = buf || req.rawBody;
  
    this.xSignature = (req.headers['x-signature'] || '').split(' ');
    this.signature = base64url.toBuffer(this.xSignature[0] || '');
    this.publicKey = base64url.toBuffer(this.xSignature[1] || '');
    this.endorsement = base64url.toBuffer(this.xSignature[2] || '');
  
    this.date = Date.parse(req.headers.date);
  }
docs: 5 minutes 
  Create a new signature instance for the given request
  
  @constructor
  @param {object} req - Request object