Measuring Post-Quantum TLS Adoption in Brazil

• Jhonatan Jauja Ccana UFRGS
• Eder John Scheid UFRGS

DOI: https://doi.org/10.5753/errc.2026.35999

Resumo

The emergence of large-scale quantum computing threatens widely deployed public-key cryptographic algorithms used to secure Internet communications, including those employed by the Transport Layer Security (TLS) protocol. Consequently, Post-Quantum Cryptography (PQC) is being progressively incorporated into TLS, particularly through hybrid key exchange mechanisms that combine classical and post-quantum algorithms. However, the actual adoption of these mechanisms across Internet services remains insufficiently characterized, especially in emerging and regional contexts. This paper addresses this gap through a measurement study of post-quantum TLS key exchange adoption among Brazilian Internet services. We analyze the top-10,000 ranked .br domains from the Tranco list, actively probing each service to identify the negotiated TLS version and key exchange group. Our results show that TLS 1.3 is already predominant, accounting for 87.3% of the measured HTTPS services with a valid TLS version, and that 4,697 of the 8,697 services with a valid key exchange group (54.0%) negotiated a post-quantum or hybrid mechanism. This adoption is highly concentrated in a single group, X25519MLKEM768, which accounts for 98.5% of the observed PQC negotiations. These findings indicate that post-quantum or hybrid key exchange mechanisms have already reached a significant deployment scale among Brazilian Internet services.

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