Explore a conference talk on message-recovery attacks targeting Feistel-based Format Preserving Encryption (FPE) presented at the 23rd ACM Conference on Computer and Communications Security. Delve into the technical challenges of FPE, including block ciphers and typical application scenarios. Examine known plaintext attacks involving multiple messages and different tweaks. Understand the expectations, sampler, and FPE scheme construction. Learn about previous work in the field and the presenters' theorem. Investigate the dual attack approach with examples. Conclude with a discussion and Q&A session on the implications of these findings for computer security and cryptography.