Viewing Single Post From: Back -Doors. Using multiple ciphers

Viewing Single Post From: Back -Doors. Using multiple ciphers
osric	Jul 31 2009, 07:10 PM
Advanced Member Posts: 51 Group: Members Member #3,254 Joined: March 15, 2009	When you are thinking about the security of your cipher, you also have to think about managing the keys, first so that they are kept secure and second so that you can distribute them securely. This feature often becomes the central consideration. The more complex the encipherment (like re-enciphering 6 times) the more keys you have to use and the bigger is the task of disseminating the keys to all users while keeping them secure. This is not a factor if you just want to encipher things to store safely on your own computer. But it is a major factor if you are talking about a network of users, which is sending messages every day. Here you have to keep changing the keys, which means you have to keep sending them securely to all the network members. Now simplicity is at a premium. An example from the 2nd World War of key compromise was the German Diplomatic cipher, which was a One Time Pad. In theory unbreakable. In practice a German courier delivered some of the keys by mistake to an overseas British Embassy. And the US relieved a Japanese courier of other keys as he travelled from Germany back to Japan through the Panama canal. These are the sort of unforeseen events that happen in life, and undermine an otherwise secure cipher. So coming back to your example, it's probably best in a real-life situation involving many users and many messages, to choose one of the secure ciphers you mention and then focus on getting the keys safely to all users.


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