// appends a new line with computer id and signature
static S signWithComputerID(S s) {
  S computerID = getComputerID();
  s = rtrim(s) + "\n\n" + "-" + computerID();
  s = fromLines(toLines(s));
  S siged= s + "sig: " + getMySignatureForText(s);
  signed = fromLines(toLines(signed));
  ret signed;
}