iDecryptIt is a Windows only program designed to decrypt the root filesystem. It's development was on hiatus for three and a half years and is currently in the process of a complete rewrite with added features. Development historically took place on SourceForge, but is now taking place on GitHub.
The current version of iDecryptIt is 11.41.1 (build
2I22), released . It supports any version of iOS when provide with the correct key. However, only keys from iOS 11.4.1 and below (that were known at release) are included. It is available for download on SourceForge.
iDecryptIt version 1.0.0 (build
1C31) was released . Since then, there have been over 20 releases.