Shared secrets chain. Identity isolates.

When an API key leaks, the compromise cascades through every service that reuses it. With per-message signatures, each hop verifies independently — no reusable credential exists to leak.

API · Shared Secret The chain reaction

✗ One compromised credential — every downstream service exposed. Restart the chain.

ACI · Per-Message Identity The isolated signature

✓ Fresh signature per hop. No reusable credential. Compromise of one signature reveals nothing about others.

Failure mode: cascading latency

When one API call fails, retries flood the queue. Every upstream service blocks waiting for downstream confirmation. The pipeline jams up even though only one link actually failed.

API · Synchronous Pipeline The retry storm

✗ One failed call, entire pipeline blocks. Retry storms multiply traffic. Queues overflow. Upstream services timeout.

ACI · Independent Verification The isolated failure

✓ Each message verified independently. One failed signature fails one message. No shared state to jam. Traffic keeps flowing.