I have a known amount encoded in ecdhInfo. I can decrypt ecdhInfo according to this formula:
amount = 8 byte encrypted amount XOR first 8 bytes of keccak("amount" || Hs(8aR||i))
How can I get a decimal value out of this decrypted 64bit field? Or, what type of variable is it after decrypting? I am working in C and want to avoid floats.