用 Digest、簽章與 Admission Policy 建立數位信任 (Digital Trust) 證據鏈
English Abstract: Docker will fully retire Docker Content Trust (DCT) and the Notary v1 service at notary.docker.io on December 8, 2026. This article traces how DCT came about in 2015 and why it is being retired a decade later, then describes the evidence chain that replaces it: digests that pin exactly which image is deployed, signatures that prove who published it, and admission policies that let a cluster run only images that can show both. It introduces the two signing tools named in Docker's migration guidance, Notation from the Notary Project and Cosign from Sigstore, with a few basic commands for each, and compares their trust models so teams can choose a path before the shutdown. 2015 年,Docker 以 The Update Framework(TUF)與 Notary v1 推出 Docker Content Trust(DCT), DOCKER_CONTENT_TRUST=1 是許多團隊第一次替 image 映像檔加上簽章的方式。Docker 在 2026 年 6 月宣布,DCT 與 notary.docker.io 上的 Notary v1 服務將於 2026 年 12 月 8 日全面停用,理由是上游的 Notary v1 已無人維護。官方同時提到,目前只有不到 0.05% 的 Docker Hub pull 仍依賴 DCT。這個數字背後所代表...