| Title | Blind Certificate Authorities |
| Publication Type | Conference Paper |
| Year of Publication | 2019 |
| Authors | Wang, Liang, Asharov, Gilad, Pass, Rafael, Ristenpart, Thomas, shelat, abhi |
| Conference Name | 2019 IEEE Symposium on Security and Privacy (SP) |
| Keywords | account ownership, alice@domain.com, anonymity, anonymous messaging, anonymous proofs, authorisation, Authorization, blind certificate authority, certificate binding, cryptographic protocols, data privacy, digital signatures, Electronic mail, Gmail, MPC, party encrypted communications, privacy, pubcrawl, public key cryptography, public key registration, resilience, Resiliency, Scalability, SCI protocol, secure channel injection protocols, Secure-Multiparty-Computation, SMTP servers, standard email server implementations, TLS, truly anonymous systems, X.509 Certificate, zero-knowledge certificate, zero-knowledge certificate signing protocol, Zero-knowledge-Proof |
| Abstract | We explore how to build a blind certificate authority (CA). Unlike conventional CAs, which learn the exact identity of those registering a public key, a blind CA can simultaneously validate an identity and provide a certificate binding a public key to it, without ever learning the identity. Blind CAs would therefore allow bootstrapping truly anonymous systems in which no party ever learns who participates. In this work we focus on constructing blind CAs that can bind an email address to a public key. To do so, we first introduce secure channel injection (SCI) protocols. These allow one party (in our setting, the blind CA) to insert a private message into another party's encrypted communications. We construct an efficient SCI protocol for communications delivered over TLS, and use it to realize anonymous proofs of account ownership for SMTP servers. Combined with a zero-knowledge certificate signing protocol, we build the first blind CA that allows Alice to obtain a X.509 certificate binding her email address alice@domain.com to a public key of her choosing without ever revealing "alice" to the CA. We show experimentally that our system works with standard email server implementations as well as Gmail. |
| DOI | 10.1109/SP.2019.00007 |
| Citation Key | wang_blind_2019 |
Blind Certificate Authorities