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identifying-cryptographic-routines-in-binaries

Identifies cryptographic algorithms embedded in a binary by scanning for well-known constants and tables (AES S-box, SHA-256/MD5 init constants, ChaCha sigma, CRC32 table, base64 alphabet). Activates for requests to identify crypto in a binary, find AES/SHA constants, or detect which encryption algorithm a sample uses.

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含まれるファイル(4)

  • SKILL.md2.8 KB
  • LICENSE340 B
  • references/api-reference.md1.3 KB
  • scripts/analyst.py3.0 KB

SKILL.md(原文)

インストールする前に、エージェントに与えられる指示の中身を確認できます。

Identifying Cryptographic Routines in Binaries

When to Use

  • You need to determine which cryptographic algorithms a sample implements (ransomware crypto, C2 encryption, config protection) by locating constant tables.
  • You want fast triage before manually reversing the crypto routine.

Do not use constant detection as proof of a specific mode/usage — it identifies the primitive, not how it is applied. This skill reads the binary statically and executes nothing.

Prerequisites

  • The binary (read inertly).

Safety & Handling

  • Read bytes statically; treat the sample as malicious data.

Workflow

Step 1: Scan for crypto constants

python scripts/analyst.py scan sample.bin

Searches for AES S-box/Te tables, SHA-256 H/K init constants, MD5 init, ChaCha/Salsa expand 32-byte k sigma, the CRC32 polynomial table, and the base64 alphabet, reporting offsets.

Step 2: Corroborate with imports/strings

Pair constant hits with crypto API imports (CryptDecrypt, BCryptEncrypt, EVP_*) or library strings to confirm.

Step 3: Locate the routine

Use the constant offset to find the referencing function for deeper reversing/key extraction.

Step 4: Document

Record which primitives are present and where, mapping to behavior (e.g., AES → file encryption).

Validation

  • Each hit references a real, named constant table (not a coincidental byte run).
  • Detected primitives are corroborated by imports/strings where possible.
  • Offsets point into the binary and can be navigated in a disassembler.

Pitfalls

  • Statically linked crypto libraries adding constants unused by the malware's logic.
  • Custom/modified S-boxes evading exact-match detection.
  • Assuming AES presence implies ransomware — corroborate with behavior.

References

レビュー

まだレビューはありません。使ってみた感想をお寄せください。

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