Use Asymmetric Key Cryptography
Asymmetric key encryption requires the generation of a public and private key, allowing the message to be encrypted with a "public" key but only decrypted using a "private" key.
Generate an asymmetric key pair.
keys = GenerateAsymmetricKeyPair
Encrypt the message using the public key.
encrypted = Encrypt[keys["PublicKey"], "The gold is located off the coast of Honduras."]
The message cannot be decrypted using the public key that encrypted it. The private key must be used.