basE91 is an advanced method for encoding binary data as ASCII characters. It is similar to base64, but is more efficient. The overhead produced by basE91 depends on the input data. It amounts at most to 23% (versus 33% for base64) and can range down to 14%, which typically occurs on 0-byte blocks.
For more information see http://base91.sourceforge.net/
The current Rust implementation is provided under the dual MIT/Apache2 license.
The original basE91 has been developed by Joachim Henke, and is released as free software under the terms of the BSD license