[ci-scan] Test failure: System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext

## Build Information
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1563837
Build error leg or test failing: android-arm Release AllSubsets_CoreCLR - System.Security.Cryptography.Tests
Recurs in follow-up build https://dev.azure.com/dnceng-public/public/_build/results?buildId=1564198 (runtime-extra-platforms, def 154).

KBE authoring guidance (ci-failure-scan)

- `Error Details` is for readers. Paste the full exception, stack trace, or build error excerpt so the failure is understandable without opening the raw log.
- Build Analysis parses only the single JSON block under `Error Message`.
- `ErrorMessage` is a case-sensitive ordinal `String.Contains` substring copied verbatim from the failing log.
- Set `BuildRetry` to `true` only for a clear infrastructure retry case. `ExcludeConsoleLog` disables Helix console-log scanning.

## Error Details

```
[FAIL] System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext
Test name: System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext(testCase: NIST GCM Spec test cases - 2 (128/96/128/128/0))
Exception messages: Assert.Throws() Failure: Exception type was not an exact match
Expected: typeof(System.Security.Cryptography.AuthenticationTagMismatchException)
Actual: typeof(System.Security.Cryptography.CryptographicException)
```

The AES-GCM tampered-ciphertext test expects an `AuthenticationTagMismatchException` but the mobile crypto backend throws the base `CryptographicException` instead.

## Error Message

```json
{
"ErrorMessage": [
"[FAIL] System.Security.Cryptography.Tests.AesGcmTests",
"Expected: typeof(System.Security.Cryptography.AuthenticationTagMismatchException)",
"Actual: typeof(System.Security.Cryptography.CryptographicException)"
],
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

Agentic workflow metadata (ci-failure-scan)

Workflow artifact: ci-failure-scan
Artifact kind: kbe-verification
Verified match count: 1 hits in failure.log

> Generated by [CI Outer-Loop Failure Scanner](https://github.com/dotnet/runtime/actions/runs/32728967403) · opus48 · 573.8 AIC · ⌖ 11.3 AIC · ⊞ 20.7K · [◷](https://github.com/search?q=repo%3Adotnet%2Fruntime+is%3Aissue+%22gh-aw-workflow-call-id%3A+dotnet%2Fruntime%2Fci-failure-scan%22&type=issues)

### Report

|Build|Repository|Test|Pull Request|
|---|---|---|---|
|[1594486](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594486)|dotnet/runtime|[System.Security.Cryptography.Tests.WorkItemExecution](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594486&view=ms.vss-test-web.build-test-results-tab&runId=44015986&resultId=165862)||
|[1580801](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1580801)|dotnet/runtime|[System.Security.Cryptography.Tests.WorkItemExecution](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1580801&view=ms.vss-test-web.build-test-results-tab&runId=43616302&resultId=166867)||
|[1572439](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1572439)|dotnet/runtime|[System.Security.Cryptography.Tests.WorkItemExecution](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1572439&view=ms.vss-test-web.build-test-results-tab&runId=43314952&resultId=200517)|dotnet/runtime#132887|
|[1571812](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1571812)|dotnet/runtime|[System.Security.Cryptography.Tests.WorkItemExecution](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1571812&view=ms.vss-test-web.build-test-results-tab&runId=43288926&resultId=234769)||
|[1567845](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567845)|dotnet/runtime|[System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1567845&view=ms.vss-test-web.build-test-results-tab&runId=43175102&resultId=200730)||
|[1566157](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1566157)|dotnet/runtime|[System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1566157&view=ms.vss-test-web.build-test-results-tab&runId=43123262&resultId=186874)||
|[1564198](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1564198)|dotnet/runtime|[System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1564198&view=ms.vss-test-web.build-test-results-tab&runId=43067448&resultId=185563)||
|[1563837](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1563837)|dotnet/runtime|[System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1563837&view=ms.vss-test-web.build-test-results-tab&runId=43058378&resultId=184487)||
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|1|8|

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1563837
**Error message validated:** `[[FAIL] System.Security.Cryptography.Tests.AesGcmTests Expected: typeof(System.Security.Cryptography.AuthenticationTagMismatchException) Actual: typeof(System.Security.Cryptography.CryptographicException)`]
**Result validation:** :white_check_mark: Known issue matched with the provided build.
**Validation performed at:** 8/28/2026 11:48:29 AM UTC