This is a paper detailing the rcrypt packer. This packer makes use of timelock puzzles and anti-analysis methods to frustrate AV detection via sandboxes and reverse engineering.
You can download it from the following link: https://packetstormsecurity.com/files/download/124578/rcrypt.pdf
Source: https://packetstormsecurity.com/files/124578/Analysis-Of-The-Rcrypt-Packer.html