A cornerstone of payment channels seems to be the idea of pre-images and their secret being communicated through the network. But when it comes to the definition of the pre-image itself, and its properties in terms of how it works within a technical system, such as payment channels, there is little information anywhere. The closest I came to information about pre-image was the mathematical description of it here:
https://en.wikipedia.org/wiki/Image_%28mathematics%29#Inverse_imageWhen talking in terms of cryptography, anything I have been able to find was how pre-image is put together as a pre-image attack on hash functions, but not a description of how the pre-image itself, and its construction for being used as a secret in for example payment channels actually works.
Anyone care to chip in some info on pre-image and how it relates to the crypto/hash of payment channels in more details?