# Decrypt AES-128 with key file but missing IV? [duplicate]

I want to decrypt a file that has been encrypted using AES-128 in CBC mode using OpenSSL. I got the “.key” file – which is 32 digits – but when I try to decrypt with OpenSSL, the program asks me for “-iv” and I don't know the IV of that file so it won't decrypt. Is there is any other way to decrypt the file without knowing the IV?

I tried with another file of which I have the correspondent IV and it works, and when I don't supply that IV, the decryption fails too.

By the way: is there anyway to know what type of encryption was used to encrypt a file?

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## marked as duplicate by e-sushi, figlesquidge, DrLecter, Gilles, rathApr 1 '14 at 21:33

Sorry is IV NO VI :P –  BelindaSchull Apr 1 '14 at 16:42
Try ECB mode, and then try the all-zero IV. $\;$ –  Ricky Demer Apr 1 '14 at 17:26
@RickyDemer And how's that going to help her decrypt the file that's already encrypted using CBC with a IV she doesn't know/have? –  e-sushi Apr 1 '14 at 17:27
Oh, I didn't notice the CBC mode part. $\:$ The all-zero IV would be a workable "default", such as if the key was only used once. $\;\;\;\;$ –  Ricky Demer Apr 1 '14 at 17:30