Full DES-56 Key Search Costs $1.2M on AWS

A new paper puts the cost of a full DES-56 key search at about $1.2 million on standard AWS instances, per arXiv 2607.23443.

DES has been considered broken since 1998, but this measurement turns that into a concrete number. The paper shows the same outcome no longer needs custom hardware, just rented cloud instances and a budget inside a well-funded attacker's reach.

Researchers benchmarked 37 c6i.2xlarge instances, measuring 2.91 million keys checked per second on each one, about 108 million keys a second combined. They averaged the numbers across 15 trials.

Small-offset attacks, where the correct key sits near the start of the search space, run in 116.8±20.1 seconds on average. That runtime is dominated by roughly 90 seconds of instance boot latency, at a cost of $0.41 per attempt.

Scale that up and the economics get uncomfortable. Those 37 instances alone would need about 21 years to exhaust the full 2^56 keyspace. The search is embarrassingly parallel, though. Renting a fleet large enough to finish in about a day brings the total bill to roughly $1.2 million. That's well inside a well-funded attacker's budget for standard rented capacity.

That price tag is the real update. DES stopped being cryptographically safe decades ago; what changes here is who can afford to break it. A $1.2 million bill on standard AWS capacity is no longer a nation-state threshold. It's within reach of any well-funded attacker.