Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2021/02/medieval-security-techniques.html

Sonja Drummer describes (with photographs) two medieval security techniques. The first is a for authentication: a document has been cut in half with an irregular pattern, so that the two halves can be brought together to prove authenticity. The second is for integrity: hashed lines written above and below a block of text ensure that no one can add additional text at a later date.