An attacker can obtain a valid TLS certificate for a domain
by hijacking communication between a certificate authority
(CA) and a victim domain. Performing domain validation
from multiple vantage points can defend against these
attacks. We explore the design space of multi-vantage-point
domain validation to achieve (1) security via sufficiently
diverse vantage points, (2) performance by ensuring low
latency and overhead in certificate issuance, (3) manageability
by complying with CA/Browser forum requirements, and
requiring minimal changes to CA operations, and (4) a
low benign failure rate for legitimate requests. Our open-
source implementation was deployed by the Let’s Encrypt
CA in February 2020, and has since secured the issuance
of more than half a billion certificates during the first year
of its deployment. Using real-world operational data from
Let’s Encrypt, we show that our approach has negligible
latency and communication overhead, and a benign failure
rate comparable to conventional designs with one vantage
point. Finally, we evaluate the security improvements using a
combination of ethically conducted real-world BGP hijacks,
Internet-scale traceroute experiments, and a novel BGP
simulation framework. We show that multi-vantage-point
domain validation can thwart the vast majority of BGP attacks.
Our work motivates the deployment of multi-vantage-point
domain validation across the CA ecosystem to strengthen
TLS certificate issuance and user privacy.
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Let's Encrypt: An Automated Certificate Authority to Encrypt the Entire Web
Let's Encrypt is a free, open, and automated HTTPS certificate authority (CA) created to advance HTTPS adoption to the entire Web. Since its launch in late 2015, Let's Encrypt has grown to become the world's largest HTTPS CA, accounting for more currently valid certificates than all other browser-trusted CAs combined. By January 2019, it had issued over 538 million certificates for 223 million domain names. We describe how we built Let's Encrypt, including the architecture of the CA software system (Boulder) and the structure of the organization that operates it (ISRG), and we discuss lessons learned from the experience. We also describe the design of ACME, the IETF-standard protocol we created to automate CA--server interactions and certificate issuance, and survey the diverse ecosystem of ACME clients, including Certbot, a software agent we created to automate HTTPS deployment. Finally, we measure Let's Encrypt's impact on the Web and the CA ecosystem. We hope that the success of Let's Encrypt can provide a model for further enhancements to the Web PKI and for future Internet security infrastructure.
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- Award ID(s):
- 1518888
- NSF-PAR ID:
- 10222849
- Date Published:
- Journal Name:
- CCS '19: Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security
- Page Range / eLocation ID:
- 2473 to 2487
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)An attacker can obtain a valid TLS certificate for a domain by hijacking communication between a certificate authority (CA) and a victim domain. Performing domain validation from multiple vantage points can defend against these attacks. We explore the design space of multi-vantage-point domain validation to achieve (1) security via sufficiently diverse vantage points, (2) performance by ensuring low latency and overhead in certificate issuance, (3) manageability by complying with CA/Browser forum requirements, and requiring minimal changes to CA operations, and (4) a low benign failure rate for legitimate requests. Our opensource implementation was deployed by the Let's Encrypt CA in February 2020, and has since secured the issuance of more than half a billion certificates during the first year of its deployment. Using real-world operational data from Let's Encrypt, we show that our approach has negligible latency and communication overhead, and a benign failure rate comparable to conventional designs with one vantage point. Finally, we evaluate the security improvements using a combination of ethically conducted real-world BGP hijacks, Internet-scale traceroute experiments, and a novel BGP simulation framework. We show that multi-vantage-point domain validation can thwart the vast majority of BGP attacks. Our work motivates the deployment of multi-vantage-point domain validation across the CA ecosystem to strengthen TLS certificate issuance and user privacy.more » « less
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1145/3319535.3363192
