用上了 ECDSA 证书

是的，我醒了。

用了几年 Let’s Encrypt 的 RSA-2048 泛域名证书，最近试着在家里的路由器上用 acme.sh 签证书的时候（当然，神奇的移不动网络不会给我机会），才发现 README.md 里有

10. Issue ECC certificates

Let's Encrypt can now issue ECDSA certificates.

And we support them too!

Just set the keylength parameter with a prefix ec-.

For example:

Single domain ECC certificate

acme.sh --issue -w /home/wwwroot/example.com -d example.com --keylength ec-256

SAN multi domain ECC certificate

acme.sh --issue -w /home/wwwroot/example.com -d example.com -d www.example.com --keylength ec-256

Please look at the keylength parameter above.

Valid values are:

1. ec-256 (prime256v1, "ECDSA P-256")
2. ec-384 (secp384r1, "ECDSA P-384")
3. ec-521 (secp521r1, "ECDSA P-521", which is not supported by Let's Encrypt yet.)

这么一段。在 官方WIP文档 里也有

ECDSA Signing Support

• Enabled: February 10, 2016

Added the ability for Let’s Encrypt to sign ECDSA keys with Let’s Encrypt’s RSA intermediates. Support for signing ECDSA keys with a full ECDSA cert chain will be added later.

说明早就可以签 ECDSA 证书了，而里面写着的

ECDSA Root and Intermediates

Currently Let’s Encrypt only signs end-entity certificates with RSA intermediates. We now have an ECDSA root and intermediates, but still need to submit them to root programs and integrate them into our issuance system.

只是根证书一直在咕而已。

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Security/Server Side TLS - MozillaWiki 里写着

We recommend ECDSA certificates using P-256, as P-384 provides negligible improvements to security and Ed25519 is not yet widely supported

Is there any benefit in including the P-384 curve in the Modern suite? · Issue #190 · mozilla/server-side-tls · GitHub

Its same reason most browsers prefer cipher suites with AES-128 first and then try AES-256. Performance/battery usage, balanced approach

所以我选择签发 P-256 --keylength ec-256。

我一直在用 LNMP 一键安装包，它也自带安装 acme.sh。由于我已经有 RSA-2048 的泛域名证书在用，不知道再签 ECDSA 泛域名会发生什么，于是我首先使用了测试服务器签发

Usage: acme.sh ... [parameters ...]
Commands:
--staging, --test Use staging server, for testing.

结果发现 acme.sh 生成了新的 _ecc 目录存储 ECDSA 证书，与 RSA 证书目录在相同的目录下，就很方便。于是我又删除了测试生成的证书，重新正式签署证书，就同时拥有了可用的 RSA 和 ECDSA 泛域名证书。

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一番搜索后发现，我们可以同时在 ssl 配置中放入两种证书

ssl_certificate rsa.cer;
ssl_certificate_key rsa.key;
ssl_certificate ecc.cer;
ssl_certificate_key ecc.key;

nginx 会根据 ClientHello 自动选择，就很方便。

ssl 配置依旧使用 Mozilla SSL Configuration Generator。

反正写的是废文，就不整 TOC（table of content）了