Only with the proper Encryption key, without that it's lost forever. Encryption uses a different algorithm every time, and only the key generated at the time of encryption can decrypt that file.
This really depends on how they have been encrypted, and which software tool they have been encrypted with. Usually, however, encrypted files are decrypted by entering a password.
You can try some softwares ,such as Password Unlocker ,Rar Password unlocker and so on.
You can find them though google.
I hope this information will be helpful.Thanks.
