Using the signature on the card as a verification method has a number of security flaws, the most obvious being the relative ease with which cards may go missing before their legitimate owners can sign them. Another involves the erasure and replacement of legitimate signature, and yet another involves the forgery of the correct signAugust 1986 |title=How to prove yourself: Practical solutions to identification and signature problems | journal=Conference on the Theory and Application of Cryptographic Techniques |volume=263|pages=186–194| doi =10.1007/3-540-47721-7| series =Lecture Notes in Computer Science| isbn =978-3-540-18047-0| s2cid =26467387}}</ref>