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</o:shapelayout></xml><![endif]--></head><body lang=EN-AU link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>The current idea for account porting is for the Old OP to provide a single token (which I’ll call port_token_plain) to the New OP; the New OP encrypts it (for the Old OP) before passing the ciphertext (port_token) to an RP; the RP passes it onto the Old OP; the Old OP decrypts it to retrieve the original token and returns the RP-specific subscriber id to the RP.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The per-RP (actually per-sector-id) encryption is necessary to preserve the privacy of pairwise subs.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>An open question is how to do the encryption.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Option 1: public key and algorithm from Old OP metadata.<o:p></o:p></p><p class=MsoNormal>The port_token seen by an RP could be a JWE (compact encoding?).<o:p></o:p></p><p class=MsoNormal>One downside is that the encryption does not authenticate that is was done by the New OP.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Option 2: symmetric encryption with secret shared by the New OP and Old OP (such as the New OP’s client_secret used in calls to Old OP).<o:p></o:p></p><p class=MsoNormal>The port_token seen by an RP would be the ciphertext from an AEAD algorithm, keyed with the client_secret, using the iss and sector_id in the additional authenticated data.<o:p></o:p></p><p class=MsoNormal>This approach saves a few bytes, avoids some public key crypto, and avoids a metadata lookup to get a public key. A downside is that client_secret is not designed to be used as an AEAD secret key.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Any preferences?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='mso-fareast-language:EN-AU'>--<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-AU'>James Manger<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>