[null,null,["最后更新时间 (UTC)：2025-07-25。"],[[["\u003cp\u003eGoogle Public DNS offers DNS resolution over TLS to enhance privacy and security between clients and resolvers, protecting against eavesdropping and spoofing.\u003c/p\u003e\n"],["\u003cp\u003eDNS-over-TLS operates using strict or opportunistic privacy profiles, with strict requiring authenticated connections to a specific server and opportunistic allowing fallback to unencrypted DNS if TLS fails.\u003c/p\u003e\n"],["\u003cp\u003eClient systems using DNS-over-TLS establish a secure connection by verifying the server's identity through TLS certificates, ensuring data is exchanged over an encrypted channel.\u003c/p\u003e\n"],["\u003cp\u003eGoogle Public DNS supports standards such as TLS 1.3, TCP Fast Open, and DNS Transport over TCP to provide a high-quality and low-latency service.\u003c/p\u003e\n"],["\u003cp\u003eUsers can configure DNS-over-TLS on devices running Android 9 or higher and also utilize it with the IPv6-only Google Public DNS64 service, though the latter is not recommended for mobile devices on multiple networks.\u003c/p\u003e\n"]]],["DNS-over-TLS encrypts DNS queries and responses, enhancing privacy and security. It operates in two profiles: *strict* and *opportunistic*. Strict requires secure TLS connection verification on port 853, failing if validation fails. Opportunistic attempts secure connection on 853 but falls back to unsecured port 53 if it fails, without validating the server. Clients using strict profile resolve the server name, establish a TLS connection on port 853, and validate the server's certificate. Google Public DNS supports this method and follows related RFC specifications.\n"],null,["# DNS-over-TLS\n\nIntroduction\n------------\n\nTraditional DNS queries and responses are sent over UDP or TCP without\nencryption.\nThis is vulnerable to eavesdropping and spoofing\n(including DNS-based Internet filtering).\nResponses from recursive resolvers to clients are the most vulnerable to\nundesired or malicious changes, while communications between recursive resolvers\nand authoritative name servers often incorporate\n[additional protection](/speed/public-dns/docs/security#mitigations).\n\nTo address these problems, Google Public DNS offers DNS resolution over\nTLS-encrypted TCP connections as specified by [RFC 7858](https://tools.ietf.org/html/rfc7858).\nDNS-over-TLS improves privacy and security between clients and resolvers. This\ncomplements DNSSEC and protects DNSSEC-validated results from modification or\nspoofing on the way to the client.\n\nHow it Works\n------------\n\n| **Note:** This section gives an overview of DNS-over-TLS operation when talking to the Google Public DNS resolver (with the name `dns.google`). If you are interested in more details, please read the RFCs [Specification for DNS over Transport Layer Security](https://tools.ietf.org/html/rfc7858) and [Usage Profiles for DNS over TLS and DNS over DTLS](https://tools.ietf.org/html/rfc8310).\n\nA client system can use DNS-over-TLS with one of [two profiles](https://tools.ietf.org/html/rfc8310#section-5):\n*strict* or *opportunistic* privacy. With the strict privacy profile, the user\nconfigures a DNS server name (the *authentication domain name* in\n[RFC 8310](https://tools.ietf.org/html/rfc8310#section-2))\nfor DNS-over-TLS service and the client must be able to create a secure TLS\nconnection on port 853 to the DNS server. Failure to establish a secure\nconnection is a hard error and will result in no DNS service for the client.\n\nWith the opportunistic privacy profile, the DNS server IP address may be\nconfigured directly by the user or obtained from the local network (using DHCP\nor some other means). The client resolver attempts to establish a secure\nconnection on port 853 to the specified DNS server. If a secure connection is\nestablished, this provides privacy for the user's queries from passive observers\non the path. Since the client does not verify the authenticity of the server it\nis not protected from an active attacker.\nIf the client cannot establish a secure connection on port 853, it falls back to\ncommunicating with the DNS server on the standard DNS port 53 over UDP or TCP\nwithout any security or privacy. The use of Opportunistic Privacy is intended to\nsupport incremental deployment of increased privacy with a view to widespread\nadoption of the strict privacy profile.\n\nWhen using a strict privacy profile, stub resolvers establish a DNS-over-TLS\nconnection with the following steps.\n\n1. The stub resolver is configured with the DNS-over-TLS resolver name `dns.google`.\n2. The stub resolver obtains the IP address(es) for `dns.google` using the local DNS resolver.\n3. The stub resolver makes a TCP connection to port 853 at the one those IP address.\n4. The stub resolver initiates a TLS handshake with the Google Public DNS resolver.\n5. The Google Public DNS server returns its TLS certificate along with a full chain of TLS certificates up to a trusted root certificate.\n6. The stub resolver verifies the server's identity based on the certificates presented.\n - If the identity cannot be validated, DNS name resolution fails and the stub resolver returns an error.\n7. After the TLS connection is established, the stub resolver has a secure communication path between to a Google Public DNS server.\n8. Now the stub resolver can send DNS queries and receive responses over the connection.\n\nWhen using an opportunistic privacy profile, the client first attempts to create\na secure TLS connection to the server. This is done similarly to the above with\none important difference - no certificate validation is performed by the client.\nThis means the identity of the server cannot be trusted. If a TLS connection on\nport 853 to the server cannot be established, the stub resolver falls back to\ntalking to the DNS server on port 53.\n| **Note:** To prevent denial of service attacks and resource exhaustion on the server, Google Public DNS may close DNS-over-TLS connections that have been idle too long or when a large number of queries have been received on the connection. The next time the client needs to perform DNS queries, the stub resolver will repeat the steps above to re-establish a connection to the Google Public DNS resolver.\n\nPrivacy\n-------\n\nOur [privacy policy](/speed/public-dns/privacy) applies to the DNS-over-TLS service.\n\nOn 2019/06/27 we have re-enabled [EDNS client subnet (ECS)](/speed/public-dns/docs/ecs)\nfor the DNS-over-TLS service. ECS was disabled at the launch of the service.\n\nStandards Support\n-----------------\n\nGoogle Public DNS implements DNS-over-TLS based on [RFC 7858](https://tools.ietf.org/html/rfc7858).\nIn addition we support the following recommendations to provide a high quality\nand low-latency DNS service.\n\n- [TLS 1.3 (RFC 8846)](https://tools.ietf.org/html/rfc8446)\n- [TCP Fast Open (RFC 7413)](https://tools.ietf.org/html/rfc7413)\n- [DNS Transport over TCP Implementation Requirements (RFC 7766)](https://tools.ietf.org/html/rfc7766)\n\nStart Using It\n--------------\n\nSee [instructions](/speed/public-dns/docs/using#android) to configure it on a\ndevice with Android 9 (Pie) or higher.\n\nDNS-over-TLS is also supported for the IPv6-only\n[Google Public DNS64 service](/speed/public-dns/docs/dns64#secure). Note that configuring DNS64 for a\nmobile device that will attach to multiple networks is not recommended, as DNS64\nonly works when IPv6 is available."]]
