US Patent 11290253 Document management cryptography

Using composite cipher technology a single ciphertext C will decrypt to plaintext Pi using key Ki, and to plaintext Pj≠Pi using key Kj≠Ki, thereby a single file C will carry any number of distinct messages so that each key holder will see in C the message intended for them. Applicable for complex project management where frequent changes and large number of people are involved. Also in email systems where a single email will deliver a shared message plus individual messages to selected readers.