I'm a freshmen in cryptography and want to know more about IV reversing. There's a lot of posts about finding the passphrase with a new IV. But what about the other situation? This is for educational purposes.
I have a cypher text :
cY1Y1VPXbhUqzYLIOVR0RhUXD5l+dmymBfr1vIKlyqD8KqHUUp2I3dhFXgASdGWzRhOdTj8WWFTJ PK0k/GDEVUBDCk1MiB8rCmTZluVHImczlOXEwJSUEgwDHA6AbiCwyAU58e9j9QbN+HwEm1TPKHQ6 JrIOpdFWoYjS+cUCZfo/85Lqi26Gj7JJxCDF8PrBp/EtHLmmTmaAVWS0ID2cJpdmNDl54N7tg5TF TrdtcIplc1tDvoCLFPEomNa5booC
The corresponding plain text :
Marvin: "I am at a rough estimate thirty billion times more intelligent than you. Let me give you an example. Think of a number, any number." Zem: "Er, five." Marvin: "Wrong. You see?"
And the passphrase :
How can I use those to find the IV? The IV length is unknown.