When using a lightning channel, two sides are sending transactions representing the current state (or balance) between them, and for each state sent, they invalidate the previous state by sending a secret for a hash puzzle in a HTLC transaction.
For example, when Alice sends Bob the new state between them, it also sends a secret for the puzzle in the previous state. Bob can use it to redeem Bitcoin if Alice publishes the previous state transaction on the blockchain.
My question is - does Bob need to save all the secrets of all the previous states until the channel is settled and closed? Sounds like Bob might need to save a lot of data when having many channels.