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This may be a dumb question so please forgive me if so, but is a hash function considered one-way even if you have half of an xor'd value?

For example say I have the values R and C, both are randomly generated and the same length as the output of the hashing function H, but while R is known C should not be given only R and h below:

h = H(C⊕R)

Is there any scenario in which you could determine C from h and R or which might reduce the difficulty of brute forcing C in this format to a level you would have to worry about?

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Since both values are randomly generated, no, there are no scenarios in which you could determine C from h and R or where your ability to brute force C is made easier by having this information as opposed to just having h.

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If it were easy to get C from h and R, you could extend that to a general pre-image attack on h by choosing an arbitrary R yourself. Then you get C and now you have a pre-image.

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