Visa Inc.
Continuous space-bounded non-malleable codes from stronger proofs-of-space

Abstract:

Systems, methods, and apparatuses for protecting a secret on a device with limited memory, while still providing tamper resistance, are described. To achieve security, an encoding computer can apply a memory-hard function MHF to a secret S and determine a result Y, then determine a proof .pi. for the result Y. Then, the encoding computer can send a codeword C comprising the secret S and the proof .pi. to a decoding computer. The decoding computer can retrieve the codeword C from persistent memory and parse the secret S and the proof .pi.. The decoding device can use transient memory decode the codeword C by verifying the proof .pi. was generated with the secret S and the result Y. When the correctness of the result Y is verified, the decoding device can apply a cryptographic function to input data using the secret S then reset the transient memory.