Build 4.0.0.38 of xlsgen makes sure that encrypted XLS and XLSX files (and their variants) are re-encrypted automatically when the file is written back after an update. The re-encryption uses the same algorithms and parameters than the decryption, which means xlsgen is neutral. This comes as an expectation since there is no ground for xlsgen removing the protection in a file without the client program asking for it (by resetting the password).

Build 4.0.0.37 of xlsgen supports all cryptographic providers that may be used in order to decrypt XLS files (and their variants), namely :

- Weak Encryption (XOR)
- Office 97/2000 Compatible (RC4 + MD5)
- RC4, Microsoft Base Cryptographic Provider v1.0
- RC4, Microsoft Base DSS and Diffie-Hellman Cryptographic Provider
- RC4, Microsoft DH SChannel Cryptographic Provider
- RC4, Microsoft Enhanced Cryptographic Provider v1.0
- RC4, Microsoft Enhanced DSS and Diffie-Hellman Cryptographic Provider
- RC4, Microsoft Enhanced RSA and AES Cryptographic Provider (Prototype) (Windows XP only)
- RC4, Microsoft Enhanced RSA and AES Cryptographic Provider
- RC4, Microsoft RSA SChannel Cryptographic Provider
- RC4, Microsoft Strong Cryptographic Provider

Build 4.0.0.36 of xlsgen makes it possible to read XLSX files generated by third parties that don't quite conform to the specs, where rows and columns in sheets are not specified on a per cell basis.