Theoretically uncrackable encryption algorithm?

Most encryption algorithms are vulnerable to the "brute force" attack in theory but not in practice. For example, even 512-bit or 1024-bit encryption is theoretically crackable. It might take you 10^20 years even if you linked all computers on Earth into one massively-parallel supercomputer. Or, assuming... show more Most encryption algorithms are vulnerable to the "brute force" attack in theory but not in practice. For example, even 512-bit or 1024-bit encryption is theoretically crackable. It might take you 10^20 years even if you linked all computers on Earth into one massively-parallel supercomputer. Or, assuming each computer operation takes a finite quanta of energy, the number of operations required would be greater than the total amount of energy available in the universe.

Clearly such encryption is good enough for practical applications but it's still theoretically crackable. I was wondering if any algorithms exist which are not, meaning even if you have unlimited energy, time, memory, and speed... it won't help you at all.
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