An 831-bit encryption key is so tough that it's physically impossible to crack before the last stars in the universe burn out.
arXiv · March 17, 2026 · 2603.13654
The Takeaway
Researchers used the laws of thermodynamics and the expansion of space to calculate a hard limit on the total 'work' any computer can perform. They found that a sufficiently long key is mathematically safe from any attack until the end of the cosmic era of star formation.
From the abstract
Modern cryptography relies on keyed symmetric ciphers to ensure the secrecy and authenticity of high bandwidth data transfer. While the advent of quantum computers poses a challenge for public key cryptography, unbroken ciphers are considered safe against quantum attacks if their key is sufficiently long. However, concrete bounds on the required key length thus far remain elusive: Despite the well known asymptotic complexity of Grover's quantum search, the optimal algorithm to recover a secret k