Early Methodists pioneered symmetric-key cryptography
A follow-up to this post:
Early Methodism depended on making journals as a spiritual discipline. One would write about spiritual highs and lows, joys and concerns, struggles and sins. It’s a method that works well in therapeutic psychology: journal your life and look for patterns of problematic behavior.
Within Wesley’s method, the holy clubs shared their journals with each other. By handing over a journal to a trusted club member, you could get a viewpoint outside yourself as well as an accountability that depends on having trusted peers. This method has parallel to contemporary fitness schemes: write down everything you eat, write down every exercise you do and hand that journal over to a trainer, coach or partner for the sake of the accountability.
Unlike weight loss journals, spiritual journals contain exceptionally personal and private information. As was recently shown in Charles Wesley’s journal, the early Methodists often write in code to keep personal spiritual struggles private, as they should be. Each club member seems to have known the key to decrypting other journals so that members and only members could read them and offer counsel and advice to one another.
This informative LiveJournal entry has a good summary of the Methodist method, with information about the encrypted journals:
1) Continuous Diaries
The significance of this “Method of Holiness” is that the diary served as a tool for self examination, and included blessings, sins, detailed accounts of daily activities, books read, conversations with other Methodists, means of grace observed, including prayer time, and devotions, including an intensity gauge for many of the entries. Every hour of the day the Oxford Methodist would update the diary.
2) Comparing Diaries
The Oxford Methodists did not stop with keeping a continuous religious diary. To put oneself on a path to greater holiness they would compare and evaluate each others diaries. A secret code prohibited outsiders from understanding the diaries, insuring privacy, so the only people who could participate in the diary swapping were the Methodists. The significance of this method of holiness is sharing diaries provided the Oxford Methodist with a high degree of accountability.
This book has excerpts of journals, still showing that fellow club members’ names were obfuscated in the journals.
Presently, we would call this system symmetric-key cryptography. The interpretive key is a “shared secret” between Methodists and no one else. I can’t think of examples of shared-key cryptography older than the 18th century, so this may be the pioneering time for this technology.
Who would have thought that for all of Phil Zimmerman’s work in public-key cryptography, most of the fundamentals had been set for over two hundred years?