This post is solely concerned with the application of the public/private key concept to the subject material of this blog and does not concern itself with the general application of this concept to other cryptosystems.
The parties that intend to exchange information must agree on a sixteen-digit private key and find a secure way to share it with each other. The private key could be created by means of encoding a text phrase as elsewhere described, and then additively combining it with other encoded text such that the result gives the appearance of a random number. The private key is never revealed or recorded but is reconstructed from the text sources each time it is required.
Example:
'privatekey' encodes as 111381594208218
'youandme' encodes as 186149702102
Combined they become:
1113 8159 4208 2181
1861 4970 2102 1861
2974 2029 6300 3942 - this is the private key
(note that digits have been made up to 16 by repeating digits from the start of the sequence)
The sender of the cryptotext must randomly generate a sixteen digit public key (10-sided dice are recommended). The public key and private key are then additively combined to produce the unique message key that is used to generate the PRS for the message to be encrypted. Public keys and message keys must never be re-used.
Example:
2974 2029 6300 3942 - this is the private key
6881 1094 7375 6773 - this is the public key (generated randomly)
8755 3013 3675 9615 - this is the message key
The public key is sent as the first 16 digits of the message and precedes the cryptotext. On receipt of the message, the recipient first reconstructs the private key, having remembered the text phrases that were used to construct it. They then combine it with the public key found at the beginning of the message to discover the message key. They then use the message key, as described elsewhere, to re-create the PRS that was used to encrypt the message and proceed to decrypt, and then decode the message.
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