dezhan is an air-gapped, immutable backup vault that speaks S3. Write an object
under a retention and the vault refuses to delete or expire it early - and
"refuses" is a state machine proved with gnatprove to have
no path that deletes a retained object.
The modern ransomware playbook deletes the backups first, then encrypts. WORM and Object Lock exist to stop that - but only if the enforcement itself cannot be turned off. dezhan makes that enforcement a machine-checked theorem.
The retention rule is a SPARK state machine, and gnatprove
discharges every path on every commit: 325 checks, 0 unproved. "Immutable" is
a property of the build, not a promise in a datasheet.
Point aws-cli, restic, Veeam, Velero, or
boto3 at the endpoint. Buckets, versioning, multipart, presigned
URLs, SigV4, and Object Lock / WORM with legal hold - validated against the AWS SDK.
No external runtime dependency. Data is content-addressed, encrypted, and erasure-coded; a background scrub verifies and self-heals, and every operation is written to an append-only, hash-chained audit log.
The trusted core is written in SPARK. Each row below is expressed as a contract
and discharged by gnatprove - the CI job fails on a single unproved
check. Not tested. Proved.
| Verified component | Invariant it guarantees | How |
|---|---|---|
retention state machine |
Retention may be extended, never shortened; a retained object cannot be deleted before expiry | SPARK contracts, discharged by gnatprove |
clock-integrity guard |
A rewound or tampered system clock cannot expire a lock; the vault seals instead of releasing | proved monotonic trusted time |
append-only audit chain |
Every operation is hash-chained; recorded history cannot be rewritten undetectably | proved append-only structure |
erasure coding |
Data survives drive loss and reconstructs exactly, or is quarantined - never returned wrong | proved reconstruction |
The cryptography - SHA-256/512, ChaCha20, HMAC, Ed25519 - is implemented in-tree with no external runtime dependency, so the whole integrity path is auditable in one place.
A vault is one writer over durable storage - a single-replica StatefulSet on a
ReadWriteOnce volume. The immutability and audit-chain guarantees
assume one writer; cross-node durability comes from the StorageClass beneath it.
dezhan - the vault server. For a plain install this is all you need.dezhan-operator - reconciles a DezhanVault CR into a StatefulSet, Service, PVC, and PodDisruptionBudget.dezhan-csi - exposes a vault as PersistentVolumes, one bucket per PVC, via mountpoint-s3.
The proof gate (scripts/prove.sh) fails the build on any unproved
check. Throughput is measured against MinIO across a 3-node k3s cluster and an
on-prem VM; dezhan trades write speed for durability and stays within a small
factor on GET.
One on-prem binary, a Helm chart for the Kubernetes operator, or the image from GHCR. For a plain install you only need the server.
curl --proto '=https' --tlsv1.2 -sSf \
https://raw.githubusercontent.com/obsernetics/dezhan/main/install.sh | shhelm repo add dezhan https://obsernetics.github.io/dezhan
helm repo update
helm install dezhan dezhan/dezhandocker pull ghcr.io/obsernetics/dezhan:latestapiVersion: dezhan.obsernetics.io/v1alpha1
kind: DezhanVault
metadata:
name: my-vault
spec:
storage: 100Gi
requireAuth: true
deleteQuorum: 2 # deletes need 2 co-signatures
secretName: my-vault-secrets # DEZHAN_VAULT_KEY, DEZHAN_SECRET, ...
Reach the vault in-cluster at
http://my-vault.<namespace>.svc:8080, then point any S3
client at it. Enabling Object Lock on a bucket makes it Immutable / WORM.
Write once, keep it honest: the delete-before-expiry path is machine-checked unreachable.