Sealing is one of the oldest parts of CHERI and one of the most powerful. When I joined the project in 2012 it was integral to the early prototype call-gate mechanism. You can find this version in our 2014 tech report. It included CSealCode and CSealData instructions that assembled a pair of capabilities that could be used with the CCall instruction to perform a cross-compartment call. By our IEEE Security and Privacy 2015 paper, this had been replaced with the modern sealing mechanism that we use today.