&gt; Crypto is all or nothing. You can&#x27;t have &quot;backdoors&quot; into crypto algorithms that are secret only to the government. It is literally impossible.<p>You don&#x27;t backdoor the algorithm. You backdoor the use of the algorithm--except it is more of a front door than a back door. For instance, when the device encrypts data with a symmetric cipher, encrypt a copy of the symmetric key via a public key cipher using the FBI&#x27;s public key.<p>Variant: split the symmetric cipher key into N shares using a secret sharing algorithm, and save each share encrypted with a different public key. Include public keys from major law enforcement agencies (FBI, Interpol), and major civil rights or human rights organizations (ACLU, EFF). Design the secret sharing so that to recover the symmetric key, you need key shares from two major law enforcement agencies and from two of the civil rights organizations.