Abstract: An administrative system generates a sequence of passwords by iterative evaluation of a hash function, initiated from a private key value and continuing to a final, public key value. A current token is created that includes a current one of the passwords. A protected device tests the validity of the current password by inputting it to a hash function sub-chain. The current password is considered valid if, after hashing the current password n+1 times, where n corresponds to the number of tokens previously received, the result is a revealed value, such as a previously verified password of the public key value. At least one unit of a one-time programmable hardware device, such as processor fuses or anti-fuses, is then physically and permanently altered, thereby incrementing a count entry indicating the number of tokens received. The protected device performs a desired action only if the current password is verified.

Abstract: An administrative system generates a sequence of passwords by iterative evaluation of a hash function, initiated from a private key value and continuing to a final, public key value. A current token is created that includes a current one of the passwords. A protected device tests the validity of the current password by inputting it to a hash function sub-chain. The current password is considered valid if, after hashing the current password n+1 times, where n corresponds to the number of tokens previously received, the result is a revealed value, such as a previously verified password of the public key value. At least one unit of a one-time programmable hardware device, such as processor fuses or anti-fuses, is then physically and permanently altered, thereby incrementing a count entry indicating the number of tokens received. The protected device performs a desired action only if the current password is verified.

Abstract: Methods and kits for removing contaminants from fuel cells are disclosed. The methods include passing a removal substance through a flow channel in the cell, where the substance is selected to remove the contaminant. The contaminants can be, e.g., metallic ions or organic compounds, and the removal substance can be, e.g., acidic or alkaline solutions, chelating agents, or oxidants.