[miki90]

Hello,

here I have 2 files. One are the encrypted and the another is decrypted. Can anyone please help me to detect the algorithm? It looks like RC4 and maybe the IV are stored in the header.. but I am not sure.

Here are the files:

Encoded: https://www.sendspace.com/file/vpet8p

Decoded: https://www.sendspace.com/file/uuj2jj

[AbakBarama]

As a rule, algorithm can't be found using plaintext and ciphertext (excluding very simple cases).
You need to analyze software which encrypts/decrypts data.