hex-text is a small library for converting between ByteStrings and their representations as hexidecimal numbers encoded as Text.

When using Stripe for payments, Stripe sends a signature as a hexidecimal Text value. The cryptonite package can be used to verify the signature, but it requires ByteString values, not Text.

A ByteString is a list of bytes. A byte is a number between 0 and 255, represented by the Word8 type. In a fixed-width hexidecimal representation, the lowest byte 0 is represented by the hex string 00, and the greatest byte 255 is represented by the hex string ff. So, for example, the ByteString consisting of bytes [ 1, 2, 3, 253, 254, 255 ] is represented as 010203fdfeff.

λ> import Text.Hex (encodeHex)
λ> import Data.ByteString (pack)

λ> (encodeHex . pack) [1, 2, 3, 253, 254, 255]
"010203fdfeff"