avatar image

Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with username, password and session length
  • December 11, 2019, 10:57 AM
  • Proudly celebrating 13 years online.
  • Donate now to become a lifetime supporting member of the site and get a non-expiring license key for all of our programs.
  • donate

Author Topic: Cryptographic Wedding Rings  (Read 2788 times)


  • Supporting Member
  • Joined in 2007
  • **
  • Posts: 1,237
    • View Profile
    • Donate to Member
Cryptographic Wedding Rings
« on: September 05, 2008, 05:03 PM »
Bruce Schneier helps a friend build a crypto system for his wedding rings, and is asking for help determining their most effective use.

Screenshot - 6_09_2008 , 8_02_50 AM_thumb.png

Cory Doctorow wanted a secret decoder wedding ring, and he asked me to help design it. I wanted something more than the standard secret decoder ring, so this is what I asked for: "I want each wheel to be the alphabet, with each letter having either a dot above, a dot below, or no dot at all. The first wheel should have alternating above, none, below. The second wheel should be the repeating sequence of above, above, none, none, below, below. The third wheel should be the repeating sequence of above, above, above, none, none, none, below, below, below."

Full Story
Ideas Here (must read full story first)



  • Supporting Member
  • Joined in 2006
  • **
  • Posts: 1,061
    • View Profile
    • Donate to Member
Re: Cryptographic Wedding Rings
« Reply #1 on: September 05, 2008, 06:02 PM »
I am not a cryptographer by any stretch, but it seems to me this would be extremely cumbersome for any significant size of text.  Instead, I would do a double substitution cypher where the two parties have a defined and known key.  This key is used to decipher a second cypher that tells how to decipher the rest of the text.


Ring Cypher uses predefined key of first letter written.  Actual cypher key starts at second letter.  First line defines the cypher for the rest of the text using some substitution rule that can be predefined, or defined by the deciphered key.  It is still hardly secure, but it is a simple method to use the ring without being overly cumbersome.