The one-time pad is the only method of cryptography that has been proven to be a mathematically unbreakable encryption. A text is paired with a secret key, or one-time pad, and then encrypted by combining it with a corresponding character from the key using modular addition. If the key is kept secret, is at least as long as the text, is completely random, and is never reused in any form, the cipher will be impossible to break.
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geocachegeocachegeocachegeocachegeocachegeocachegeocachegeocachegeocache
You can validate your puzzle solution with certitude.