type: service
status: active
timestamp: 2026-06-24
tags: [service, security, encryption, age, sops-backend]

age — modern file encryption (X25519 + ChaCha20-Poly1305)

Modern file encryption (X25519+ChaCha20-Poly1305) — SOPS master-key backend, single key file

age — modern file encryption

What it is

A 2019-era file-encryption tool by Filippo Valsorda (Go-language cryptographer, ex-Google, ex-Cloudflare). Designed as a modern replacement for gpg --encrypt with a minimal feature set.

Algorithms: X25519 for key exchange, ChaCha20-Poly1305 for stream encryption, HKDF-SHA-256 for key derivation
Key format: a single age1... public key (~62 chars), a single AGE-SECRET-KEY-1... private key (~74 chars)
No keyring: keys are just text strings. Save them in a file, password manager, or sticky note.
Multiple recipients: a single ciphertext can be encrypted to N public keys, any one of which can decrypt.
Latest: v1.3.1 (2026)

Why we use it (instead of PGP/KMS)

Concern	age	GPG	AWS KMS
Setup time	30 sec (`age-keygen`)	30 min (keyring + web of trust)	hours (IAM + KMS policies)
Cloud dependency	None	None	AWS account
Failure modes	Lose the key file	GPG agent issues, expired subkeys, web-of-trust corruption	IAM misconfig, KMS region outage, billing
Cost	$0	$0	$0.03 / 10K decrypt requests
Multi-recipient	Yes (additive)	Yes (additive)	Yes (KMS grants)
Offline decryption	Yes, forever	Yes, forever	Requires AWS reachable

For a solo dev with no compliance requirement, age wins on simplicity. The cost is real but small: it has no integration with hardware tokens, no revocation list, no formal trust model. Trade-offs we accept.

Our setup

Where the keys live:

Private key: Bitwarden CLI, item age-key, retrieved with bw get item age-key | jq -r .notes
Public key: in .sops.yaml at the umbrella root (committed, public is meant to be public)

Generate (one-time, only if rotating):

age-keygen -o ~/.config/sops/age/keys.txt    # generates new keypair
# Copy the public age1... line into .sops.yaml
# Copy the AGE-SECRET-KEY-1... into Bitwarden CLI

On a fresh machine:

bw get item age-key | jq -r .notes > ~/.config/sops/age/keys.txt
export SOPS_AGE_KEY_FILE=~/.config/sops/age/keys.txt
# Now sops -d works in any submodule

CI (GitHub Actions):

- name: Decrypt secrets
  env:
    SOPS_AGE_KEY: ${{ secrets.SOPS_AGE_KEY }}    # the private key as a single env var
  run: sops decrypt -i .env.enc

Key rotation

Rotation is a Bitwarden CLI update + a re-encrypt of every .env.enc family-wide. ~5 min if all submodules are cloned locally. We have not rotated yet (and have no scheduled rotation) — the cost of a real rotation only justifies if the current key is suspected compromised. See [[runbooks/rotate-age-key]] (write when first needed).

Anti-patterns

Storing the age private key in a repo. Bitwarden only.
Sharing the age key with collaborators. If a second human ever needs decrypt access, they get their OWN keypair, and we add their public key to .sops.yaml as a second recipient. SOPS supports multi-recipient.
Using age for streaming / large files. age is fine for files up to a few MB; for large blobs, use age-plugin-rage or another tool.
Encrypting binary files we don’t actually need encrypted. age adds ~200 bytes of overhead per file; not a big deal but pointless on already-zipped tarballs.

[[services/business/security/sops]] — the wrapper that calls age for the data-key step
[[security/sops-plus-doppler-hybrid]] — overall secrets architecture
[[rules/submodule-env-files-three-file-pattern]] — the three-file pattern that uses age

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