[hash_digest] 计算 HMAC（基于哈希的消息认证码）。 【支持算法】Sha1 / Sha224 / Sha256 / Sha384 / Sha512 / Sm3（不支持 SHAKE 系列，因 SHAKE 为 XOF 非固定长度哈希）。 【参数】 - key_in_hex：密钥 Hex（16~256 字节，即 32~512 个 hex 字符） - plain_in_hex：待认证数据 Hex（1B ~ 16MB） - required_hash_modes：字符串数组，指定 HMAC 底层哈希算法列表，默认计算全部 6 种算法 【输出】Results 字典，每个算法对应 hm...
Part of the CipherHUB Cryptography Toolkit server.
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AI agents call hmac_sum to retrieve information from CipherHUB Cryptography Toolkit without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though hmac_sum only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"hmac_sum": {}
}
}See the full CipherHUB Cryptography Toolkit policy for all 32 tools.
These attack patterns abuse exactly the kind of access hmac_sum gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
[hash_digest] 计算 HMAC（基于哈希的消息认证码）。 【支持算法】Sha1 / Sha224 / Sha256 / Sha384 / Sha512 / Sm3（不支持 SHAKE 系列，因 SHAKE 为 XOF 非固定长度哈希）。 【参数】 - key_in_hex：密钥 Hex（16~256 字节，即 32~512 个 hex 字符） - plain_in_hex：待认证数据 Hex（1B ~ 16MB） - required_hash_modes：字符串数组，指定 HMAC 底层哈希算法列表，默认计算全部 6 种算法 【输出】Results 字典，每个算法对应 hmac_sum_in_hex（HMAC Hex 编码）和 hmac_length（字节数）。 【典型用途】消息完整性验证、API 签名、密钥确认。. It is categorised as a Read tool in the CipherHUB Cryptography Toolkit MCP Server, which means it retrieves data without modifying state.
Register the CipherHUB Cryptography Toolkit MCP server in PolicyLayer and add a rule for hmac_sum: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches CipherHUB Cryptography Toolkit. Nothing to install.
hmac_sum is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the hmac_sum rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for hmac_sum. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
hmac_sum is provided by the CipherHUB Cryptography Toolkit MCP server (https://tools.cipherhub.cloud/cipherhub/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 32 CipherHUB Cryptography Toolkit tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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