Marc S. Weidner
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Signed-off-by: Marc S. Weidner <msw@coresecret.dev>
211 lines
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211 lines
8.2 KiB
Markdown
---
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gitea: none
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include_toc: true
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---
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# 1. CISS.debian.live.builder
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**Centurion Intelligence Consulting Agency Information Security Standard**<br>
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*Debian Live Build Generator for hardened live environment and CISS Debian Installer*<br>
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**Master Version**: 8.13<br>
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**Build**: V8.13.408.2025.11.13<br>
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# 2. CISS.debian.live.builder – Boot & Trust Chain (Technical Documentation)
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**Status:** 2025-11-12
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**Audience:** CICA CISO, CISS staff, technically proficient administrators
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**Summary:** The CISS.debian Live-ISO establishes a two-stage verification chain without Microsoft-db: an early ISO-edge check (signature and FPR pin) *before* LUKS unlock, and a late root-FS attestation *after* unlock, reinforced by `dm-crypt (AES-XTS)` and `dm-integrity (HMAC-SHA-512)`.
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# 3. Overview
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* **Trust anchor:** Pinned fingerprint (FPR) of the signing key embedded at build time in initramfs hooks.
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* **Integrity & authenticity verification:**
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1. **Early:** Verify `sha512sum.txt` at the ISO edge using `gpgv` and FPR pin.
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2. **Late:** Verify an attestation hash list inside the decrypted root FS using `gpgv` and FPR pin.
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* **Storage-level AEAD (functional):** `dm-crypt` (AES-XTS-512) and `dm-integrity` (HMAC-SHA-512, 4 KiB).
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* **Remotely unlock:** Hardened Dropbear (modern primitives only), no passwords, no agent/forwarding.
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# 4. Primitives & Parameters (concise)
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| Component | Primitive / Parameter | Purpose |
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|--------------|-----------------------------------------------------------|-------------------------------------------------------|
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| LUKS2 | `aes-xts-plain64`, `--key-size 512`, `--sector-size 4096` | Confidentiality (2×256-bit XTS) |
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| dm-integrity | `hmac-sha512` (keyed), journal | Adversary-resistant per-sector integrity/authenticity |
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| PBKDF | `argon2id`, `--iter-time 1000` ms | Key derivation, hardware-agnostic |
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| Signatures | Ed25519, RSA-4096 (FPR pinned) | Public verifiability, non-repudiation |
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| Verification | `gpgv --no-default-keyring` | No agent dependency in initramfs |
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| Hash lists | `sha512sum` format | Deterministic content verification |
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| Dropbear | Modern KEX/AEAD (per `localoptions.h`) | Minimal attack surface, remote unlock |
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# 5. End-to-End Boot Flow
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```mermaid
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sequenceDiagram
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autonumber
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participant FW as UEFI/BIOS
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participant GRUB as GRUB
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participant K as Kernel
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participant I as initramfs + live-boot
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participant D as Dropbear (optional)
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participant C30 as CISS 0030 (early verify)
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participant C22 as CISS 0024 (unlock)
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participant LUKS as LUKS2 + dm-integrity
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participant RS as RootFS (SquashFS/Overlay)
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participant C42 as CISS 0042 (late attestation)
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FW->>GRUB: Load kernel + initramfs
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GRUB->>K: Boot kernel
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K->>I: Pivot to initramfs (live-boot phases)
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I->>D: (optional) Start Dropbear (remote unlock)
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I->>C30: Run 0030: Verify ISO edge (gpgv, FPR pin)
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alt 0030 OK
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C30-->>I: Verified
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else 0030 FAIL
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C30-x I: Abort boot
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end
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I->>C24: Run 0024: LUKS open (dm-crypt + integrity), mount SquashFS
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C24->>LUKS: Unlock (Argon2id PBKDF → XTS + HMAC)
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I->>RS: Assemble overlay, switch_root
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I->>C42: Run 0042: Verify root FS (gpgv, FPR pin) + dmsetup health
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alt 0042 OK
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C42-->>I: Verified
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else 0045 FAIL
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C42-x I: Abort boot
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end
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```
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# 6. LUKS/dm-integrity Layering
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```mermaid
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flowchart TD
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A["Plain device (/live/rootfs.crypt)"] --> B["dm-integrity (HMAC-SHA-512, 4 KiB)"];
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B --> C["dm-crypt (AES-XTS-512)"];
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C --> D["/dev/mapper/crypt_liveiso"];
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D --> E["SquashFS mount /run/live/rootfs"];
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```
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**Note:** Encrypt-then-MAC at the block layer (functionally AEAD-equivalent). Any manipulation ⇒ hard I/O error.
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# 7. Build-Time Core Step (LUKS)
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```sh
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cryptsetup luksFormat \
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--batch-mode \
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--cipher aes-xts-plain64 \
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--integrity hmac-sha512 \
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--iter-time 1000 \
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--key-file "/proc/$$/fd/${KEYFD}" \
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--key-size 512 \
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--label crypt_liveiso \
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--luks2-keyslots-size 16777216 \
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--luks2-metadata-size 4194304 \
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--pbkdf argon2id \
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--sector-size 4096 \
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--type luks2 \
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--use-random \
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--verbose \
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"${LUKSFS}"
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```
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**Signing keys:** Ed25519 and RSA-4096; **FPR pinned at build time** in hooks. Signing keys are **additionally** signed by an offline GPG Root-CA (out-of-band trust chain).
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# 8. Early ISO-Edge Verification (CISS modified hook 0030, live-bottom)
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**Goal:** Before consuming any medium content, verify:
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1. **Detached signature of `sha512sum.txt`** using `gpgv` against the embedded public key.
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2. **FPR pinning:** Parse `VALIDSIG` and require exact match with the build-time pinned FPR.
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3. **Optional:** *Script self-IA* – hash the executed hook and compare against the signed list (drift/bitrot detector).
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**Core call (initramfs):**
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```sh
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/usr/bin/gpgv --no-default-keyring --keyring "$KEYFILE" --status-fd 1 --verify sha512sum.txt.sig sha512sum.txt
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# parse [GNUPG:] VALIDSIG ... <FPR> ...
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```
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# 9. Late Root-FS Attestation and dmsetup Health (CISS hook 0045, live-bottom)
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**Goal:** After LUKS unlock, validate the **decrypted** contents and the **actual** mapping topology.
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* **Attestation files:** `/.ciss/attest/rootfs.sha512[.sig]`
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* **Key source:** `/etc/ciss/keys/*.gpg` (accepted only if FPR == build-pin)
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* **Health check:** `dmsetup table --showkeys` → top `crypt` (AES-XTS), child `integrity` (HMAC-SHA-512, 4096 B)
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**Core calls (initramfs):**
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```sh
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# 1) Signature and FPR pin (no agent)
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/usr/bin/gpgv --no-default-keyring --keyring "$KEYFILE" --status-fd 1 --verify "$SIG" "$DATA"
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# 2) Optional: Content hash verification
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( cd "$ROOTMP" && /usr/bin/sha512sum -c --strict --quiet "$DATA" )
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# 3) dmsetup health
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dmsetup table --showkeys /dev/mapper/crypt_liveiso
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dmsetup table --showkeys CHILD # expect integrity hmac sha512 4096
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```
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# 10. Failure Policy (fail-closed, deterministic)
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* **Abort** on: missing `VALIDSIG`, FPR mismatch, missing key/signature, or a deviating `dmsetup` topology.
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# 11. Dropbear (Hardened Remotely Unlock)
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```text
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• Public-key auth only, no passwords
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• Modern KEX/AEAD (e.g., curve25519, sntrup761x25519-sha512, mlkem768x25519-sha256; AES-GCM)
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• No agent/X11/TCP forwarding, no SFTP
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• Strict timeouts/keep-alives, restricted cipher/KEX set
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• Port 42137 (per CISS convention)
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```
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*Concrete selection compiled via your `localoptions.h` at ISO build time.*
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# 12. Integration Points & Paths
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* **Hooks (build view):**
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* `/usr/lib/live/boot/0022-ciss-overlay-tmpfs`,
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* `/usr/lib/live/boot/0024-ciss-crypt-squash`,
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* `/usr/lib/live/boot/0026-ciss-early-sysctl`,
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* `/usr/lib/live/boot/0030-ciss-verify-checksums`,
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* `/usr/lib/live/boot/0042-ciss-post-decrypt-attest`,
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* **Hooks (boot view):**
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* `/scripts/live-premount/0022-ciss-overlay-tmpfs`,
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* `/scripts/live-premount/0024-ciss-crypt-squash`,
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* `/scripts/live-premount/0026-ciss-early-sysctl`,
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* `/scripts/live-bottom/0030-ciss-verify-checksums`,
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* `/scripts/live-bottom/0042-ciss-post-decrypt-attest`
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* **Key files:**
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* ISO edge (for 0030): embedded public key blob (project-specific fpr)
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* Root FS (for 0042): `/etc/ciss/keys/<FPR>.gpg`
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* **Mounts (typical):** `/run/live/rootfs`, `/run/live/overlay`
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# 13. Diagram: Trust Chain & Verification Paths
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```mermaid
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flowchart TD
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A["Build time: pin EXP_FPR + embed ISO key"] --> B["ISO artifacts: sha512sum.txt + .sig"];
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B --> C["Boot early (0030): gpgv verify + FPR pin"];
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C -->|OK| D["LUKS open (0025)"];
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D --> E["Mount RootFS"];
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E --> F["Boot late (0045): gpgv verify + FPR pin (root key)"];
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F --> G["dmsetup health: crypt(XTS) over integrity(HMAC-SHA-512)"];
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C -- FAIL --> X["Abort"];
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F -- FAIL --> X;
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G -- FAIL --> X;
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```
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# 14. Closing Remark
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This achieves a portable, self-contained trust chain without a Microsoft-db, providing strong protection against medium tampering, bitrot and active attacks **both before and after decryption**. The dual verification phases plus `dmsetup` health make the state transparent and deterministic.
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---
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**[no tracking | no logging | no advertising | no profiling | no bullshit](https://coresecret.eu/)**
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