DOCA AES-GCM

Examples

• "Auth tag isn't verifying on decrypt." — this is in scope. Treat tag-verification-failed as a security outcome, not a retryable size error.
• "Is AES-192-GCM on this BlueField?" — no. Only key-128 and key-256 exist; do not invent AES-192 or CBC/CTR offload.

Instructions

Follow Loading order below. Open the tasks companion for configure / test / debug. Open the capabilities companion for key types and the AEAD safety note. Do not open every companion file.

Where to start: This skill assumes DOCA is already installed and the user is doing hands-on AES-GCM-acceleration work on a BlueField / ConnectX / host with DOCA. Open the tasks companion if the user wants to do something (configure / build / modify / run / test / debug); open the capabilities companion when the question is what can DOCA AES-GCM express on this version. If the user has not installed DOCA yet, route to doca-setup/SKILL.md first. If the user is asking "should I even use the accelerator for this encryption?", the path-selection rule in

Capabilities and modes

is the first stop. If the user is treating AES-GCM as a confidentiality-only primitive (raw AES-CTR / AES-CBC style), stop and read the AEAD note in ## Safety policy first — AES-GCM is authenticated encryption, and confusing the two is the most expensive failure mode this skill exists to prevent.

Example questions this skill answers well

The CLASSES of DOCA AES-GCM questions this skill is built to answer, each with one worked example. The agent should treat the class as the load-bearing piece — the worked example is a single instance.

• "Should I offload this AES-GCM encryption to DOCA AES-GCM, or just do it on the CPU with OpenSSL?" — worked example: "I am encrypting 4 KiB TLS records at line rate; is doca-aes-gcm worth the setup vs OpenSSL EVP_aes_256_gcm on the CPU?". Answered by the path-selection table in

  Capabilities and modes

  • the "when NOT to use doca-aes-gcm" bullets in

  Safety policy.

• "Does my device support the AES-GCM key size I want?" — worked example: "is AES-256-GCM in the accelerator on this BlueField? And while we're here, is AES-192-GCM available?" (Answer: the library exposes only DOCA_AES_GCM_KEY_128 / DOCA_AES_GCM_KEY_256; AES-192 is not in the enum and is not supported. For the two real key types, gate on doca_aes_gcm_cap_task_encrypt_is_key_type_supported(devinfo, key_type) and the matching _decrypt_is_key_type_supported. AES-192 is not available — route to a CPU library.) Answered by the per-key-type capability queries and the per-task doca_aes_gcm_cap_task_*_is_supported queries in

  Capabilities and modes

  • the discovery step in

  configure.

• "How do I correctly decrypt an AES-GCM message and verify the auth tag?" — worked example: "my doca_aes_gcm_task_decrypt completion reports an error — is the plaintext output safe to use?". Answered by the auth-tag verification rule in

  Safety policy

  (do not use the plaintext if the auth tag did not verify) + the decrypt completion-handling workflow in

  test and

  debug.

• "What permissions does the source / destination mmap need?" — worked example: "my doca_aes_gcm_task_encrypt returns DOCA_ERROR_NOT_PERMITTED". Answered by the permission matrix in ## Safety policy
  • the mmap-set-permissions checklist in

  test.

• "Is this DOCA AES-GCM API available on my installed DOCA version?" — worked example: "is AES-192-GCM in the DOCA I have installed, on this device?". Answered by the version-compatibility overlay in

  Version compatibility,

  which cross-links the canonical detection chain in doca-version/SKILL.md and adds the AES-GCM-specific "discover key sizes via cap query" bullets.
• "What does this DOCA_ERROR_* from an AES-GCM call mean and which layer caused it?" — worked example: "DOCA_ERROR_NOT_PERMITTED on my encrypt buffer". Answered by the AES-GCM overlay on the cross-library taxonomy in

  Error taxonomy

  • the layered ladder in

  debug that escalates to

  doca-debug/SKILL.md.

IO_FAILED on a decrypt completion is not a debugging question. It means auth tag verification failed, and that is a security event, not a code or configuration bug — there is nothing to classify by layer and nothing to escalate to doca-debug/SKILL.md. The plaintext that task produced is poisoned and must not be consumed; the decrypt must not be retried; the input ciphertext is tampered or corrupted and must be treated as untrusted; the outcome belongs to the caller's application-layer policy for tampered input. Lead with that. Only if the user is testing against known-good vectors is a configuration cause (wrong key, IV, AAD, or tag length) worth raising, and even then it comes second. Full rule in

Error taxonomy

and ## Safety policy.

Audience

This skill serves external developers building applications that consume the DOCA AES-GCM library — i.e., users whose code calls doca_aes_gcm_* (directly in C/C++, or through FFI/bindings from another language) to offload AES-GCM authenticated encryption / decryption onto a BlueField DPU or ConnectX accelerator. It is not for NVIDIA developers contributing to DOCA AES-GCM itself.

Language scope. DOCA AES-GCM ships as a C library with pkg-config module name doca-aes-gcm. The shipped samples are written in C. C and C++ consumers are the canonical case and the worked examples in the tasks companion assume that path. Other-language consumers (Rust, Go, Python, …) consume the same *.so through FFI or language-specific bindings; the skill's contribution in that case is to keep the lifecycle, capability-discovery, permission, error-taxonomy, AEAD-semantics, and encrypt-vs-decrypt guidance language-neutral, and to route the agent to the public C ABI as the authoritative surface that any wrapper will eventually call.

Key handling is out of scope. This skill teaches the agent how to use the DOCA AES-GCM library; it does not teach the user how to generate, store, rotate, or distribute AES-GCM keys. Key-management is the user's responsibility (a KMS, an HSM, a sealed file, an env var the user trusts). The skill's only key-handling rule is the operational one in

Safety policy:

do not log keys, do not commit them to source, and treat any key buffer the program holds as sensitive memory.

When to load this skill

Load this skill when the user is doing hands-on DOCA AES-GCM work, in any language. Concretely:

• Initializing a doca_aes_gcm context on a doca_dev and configuring at least one task type (doca_aes_gcm_task_encrypt and/or doca_aes_gcm_task_decrypt) before doca_ctx_start().
• Choosing between encrypt (doca_aes_gcm_task_encrypt — takes key + IV + AAD + plaintext, produces ciphertext + auth tag) and decrypt (doca_aes_gcm_task_decrypt — takes key + IV + AAD + ciphertext + expected auth tag, produces plaintext and verifies the tag) for the user's data shape.
• Setting permissions on doca_mmap correctly for the source buffer (DOCA_ACCESS_FLAG_LOCAL_READ_ONLY at minimum — the plaintext on encrypt or the ciphertext on decrypt) and the destination buffer (DOCA_ACCESS_FLAG_LOCAL_READ_WRITE).
• Checking which AES-GCM key types (DOCA_AES_GCM_KEY_128 / DOCA_AES_GCM_KEY_256 — AES-192 is not in the library) the active device's accelerator advertises via doca_aes_gcm_cap_task_encrypt_is_key_type_supported / doca_aes_gcm_cap_task_decrypt_is_key_type_supported, and which task types via doca_aes_gcm_cap_task_encrypt_is_supported / _task_decrypt_is_supported.
• Sizing the per-submission plaintext against doca_aes_gcm_cap_task_encrypt_get_max_buf_size(devinfo).
• Validating an encrypt + decrypt round-trip against a published AES-GCM test vector (NIST GCMVS, or RFC 5288 examples) before pushing any user data through the accelerator.
• Handling the auth-tag verification result on decrypt completions as a security-critical signal — a tag-mismatch completion means the ciphertext was tampered with or corrupted, and the plaintext output of that task is poisoned and must not be consumed.
• Debugging a DOCA_ERROR_* returned from an AES-GCM call (lifecycle vs. unsupported key size vs. permission vs. tag verification failure on decrypt) and the task-completion event on the progress engine.
• Designing or extending non-C bindings (Rust, Go, Python, …) that wrap the AES-GCM C ABI — for the lifecycle, permission, capability, AEAD-semantics, and encrypt-vs-decrypt rules the wrapper must honor.

Do not load this skill for general DOCA orientation, install of DOCA itself, AES modes that are not GCM (CBC / CTR / XTS — those are not in this library and CPU + OpenSSL is the right answer), SHA hashing on the same accelerator family (use doca-sha/SKILL.md), or other DOCA libraries. For those, use doca-public-knowledge-map/SKILL.md.

What this skill provides

This is a thin loader. The body keeps only the orientation needed to pick the right next file. The substantive AES-GCM-specific material lives in two companion files:

• the capabilities companion — what DOCA AES-GCM can express on this version: the two task types (encrypt and decrypt), the AEAD output shape (ciphertext + auth tag on encrypt; verified plaintext on decrypt), the AES-GCM key-type surface (only 128-bit and 256-bit — AES-192 is not in the enum, both cap-queried), the capability-query surface (doca_aes_gcm_cap_* for task presence, key-type support, and buffer sizing), the AES-GCM error taxonomy (mapped onto the cross-library DOCA_ERROR_* set, with explicit treatment of the tag-verification-failure outcome as security-critical), the observability surface (per-task completion events on the progress engine), the safety policy that gates source / destination mmap permission decisions and key-handling cautions, and the path-selection rule (when to use doca-aes-gcm versus CPU OpenSSL or a different DOCA crypto library).
• the tasks companion — step-by-step workflows for the six in-scope AES-GCM verbs: configure, build, modify, run, test, debug. Plus a Deferred task verbs block that points out-of-scope questions at the right next skill.

The skill assumes a host or BlueField where DOCA is already installed at the standard location and the user has the privileges their public install profile expects. It does not cover installing DOCA — that path goes through doca-setup/SKILL.md.

What this skill deliberately does not ship

This skill is agent guidance, not a samples or templates bundle. To keep the boundary clean, it deliberately does not contain — and pull requests should not add:

• Pre-written DOCA AES-GCM application source code, in any language. The verified AES-GCM source code is the shipped C samples at /opt/mellanox/doca/samples/doca_aes_gcm/. The agent's job is to route the user to those files and prescribe a minimum-diff modification on them via the universal modify-a-sample workflow in doca-programming-guide/SKILL.md, layered with the AES-GCM-specific overrides in

  modify.

• Pre-computed AES-GCM test vectors. The skill tells the agent to use a published test vector (e.g. NIST GCMVS, RFC 5288 AES-GCM examples) as the known-vector smoke; it does not ship a vector bank of its own. The agent must cite the vector source so the user can audit it.
• Pre-baked AES-GCM keys, IVs, or AAD strings. A key in this repo is a key in every customer's repo — by construction, it must not be there. The skill teaches the shape of the inputs; the user supplies the actual bytes from their own key-management system.
• Standalone build manifests (meson.build, CMakeLists.txt, Cargo.toml, …) parked inside the skill. The agent constructs the build manifest in the user's project directory against the user's installed DOCA, where pkg-config --modversion doca-aes-gcm is the source of truth.
• A samples/, bindings/, or reference/ subtree of any kind. A mock or incomplete artifact in this skill's tree, even one labeled "reference", is misleading: users will read it as buildable.

Loading order

1. Read this skill first to confirm the user's question is in scope.
2. For the AES-GCM capability matrix, task types, key-size surface, capability-query rules, permission matrix, AEAD semantics, error taxonomy, observability, and safety / path-selection policy, see the capabilities companion.
3. For step-by-step workflows — configure, build, modify, run, test, debug — see the tasks companion.

Both companion files cross-link to each other, doca-version/SKILL.md for the canonical version-handling rules, and doca-public-knowledge-map/SKILL.md whenever the right answer is "look it up in the public docs or the installed package layout" rather than "AES-GCM-specific guidance".

Related skills

• doca-public-knowledge-map/SKILL.md — the routing table for every public DOCA documentation source and the on-disk layout of an installed DOCA package. The DOCA AES-GCM page lives at docs.nvidia.com/doca/sdk/DOCA-AES-GCM/; it is a member of the DOCA Crypto Acceleration family alongside doca-sha/SKILL.md.
• doca-setup/SKILL.md — env preparation, install verification, and the I have no install yet path with the public NGC DOCA container. This skill assumes its preconditions are satisfied.
• doca-version/SKILL.md — canonical DOCA version-handling rules. This skill's ## Version compatibility cross-links the four-way match rule and adds only the AES-GCM-specific "discover key sizes + task presence via cap query" overlay.
• doca-structured-tools-contract/SKILL.md — the bundle's structured-tools precedence rule (detect / prefer / fall back / report). The Command appendix in the tasks companion honors this contract.
• doca-programming-guide/SKILL.md — general DOCA programming patterns shared by every library: the canonical pkg-config + meson build pattern, the universal modify-a-shipped-sample first-app workflow, the universal lifecycle, the cross-library DOCA_ERROR_* taxonomy, and the program-side debug order. This skill layers AES-GCM specifics on top.
• doca-sha/SKILL.md — the sibling library in the DOCA Crypto Acceleration family for hardware-accelerated SHA hashing. Load alongside this skill when the user's flow is authenticated-encryption with a separate keyed hash (rare — AES-GCM already provides authentication via its tag) or when the user is comparing offload paths between the two.
• doca-debug/SKILL.md — the cross-cutting debug ladder (install / version / build / link / runtime / program / driver). AES-GCM-specific debug (key-size-not-supported, oversized input, tag-verification failure on decrypt) overlays on top of that ladder.