Off-the-Record Messaging: Where Deniable Encryption Started

Short summary

The 2004 OTR protocol by Borisov, Goldberg, and Brewer argued PGP gets message security backwards by creating durable, transferable proof of authorship. OTR introduced forward secrecy through ephemeral Diffie-Hellman key exchanges and deniability via malleable encryption and published MAC keys, making transcripts worthless as forensic evidence. These ideas now underpin modern messaging protocols used by billions.

• •OTR's 2004 paper argued PGP destroys two properties of in-person conversation: transience and retroactive security
• •Forward secrecy via ephemeral DH keys means stolen long-term keys can't decrypt past messages
• •Deniability via malleable encryption and published MAC keys makes transcripts non-provable after the fact

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