When knowing the full content of the original message, will I be able to derive the private key from the encrypted message when the underlying encryption uses a fixed initialization vector?
Meaning if we encrypt by
Text UNENCRYPTED x Private Key =[fixed IV]=> Text ENCRYPTED, can we somehow calculate the key backwards by
Text ENCRYPTED % Text UNENCRYPTED =[fixed IV]=> Private Key, considering a fixed IV is used?
If the answer is no, please explain why this is not possible. If the answer is yes, will the calculated key really be the private key or just a local solution to this particular message, not suitable to decrypt other texts encrypted with the same unknown private key? (The latter would mean something like:
Text ENCRYPTED % Text UNENCRYPTED =[fixed IV]= Pseudo Private Key != Private Key)
(You might also note differently:
fx(Text UNENCRYPTED, Private Key) = Text ENCRYPTED, so if
fy(Text ENCRYPTED, Text UNENCRYPTED) = Private Key, how to get from the function fx to fy? If a fixed IV would not allow this, please mention some other encryption methods with which this backwards calculation would be possible)