crypto-hasher

name	crypto-hasher
description	WASM skill providing cryptographic hashing operations for VAK agents.

Crypto Hash Skill

A WebAssembly module providing cryptographic hashing operations that runs inside the VAK kernel sandbox.

Overview

This skill provides secure hashing operations for:

• SHA-256 hashing
• HMAC-SHA256 authentication codes
• Hash verification

Building

# Build for WASM target
cargo build -p crypto-hasher --target wasm32-unknown-unknown --release

# Output location
# target/wasm32-unknown-unknown/release/crypto_hash.wasm

Operations

Operation	Input	Output	Description
sha256	bytes	[u8; 32]	SHA-256 hash
sha256_hex	bytes	String	SHA-256 hash as hex string
hmac_sha256	(key, data)	[u8; 32]	HMAC-SHA256
verify_hash	(data, hash)	bool	Verify hash matches

Safety

This skill runs in the VAK WASM sandbox with:

• Epoch preemption: Automatic timeout for long operations
• Memory limits: Pooling allocator enforces memory bounds
• No secret storage: Hashes are computed but not stored

Usage Example

// From VAK kernel
let hash = kernel.execute_skill("crypto-hasher", "sha256_hex", &data).await?;

Security Considerations

• Keys should not be stored in WASM memory longer than necessary
• Use constant-time comparison for hash verification (implemented)
• Suitable for integrity checks, not for password storage

Files

• Cargo.toml - Crate configuration
• src/lib.rs - Skill implementation