Contact person: Business Client

Phone:Show

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Location: Stockholm, Sweden

Budget: Recommended by industry experts

Time to start: As soon as possible

Project description:
"I’ve built a Snap-style social media app on [login to view URL] and wired in the full Signal protocol—X3DH for the first handshake, ECDH+Double Ratchet for forward secrecy, AES-GCM-256 with HKDF-HMAC-SHA-256 for payload protection. On paper everything looks correct, yet in practice messages still slip out in plaintext or throw a “failed to send” error whenever the recipient hasn’t generated keys or an old session is corrupted.

What I need now is an experienced cryptography engineer who has actually debugged Signal-based stacks to step in right away, review my current implementation and make the encryption rock-solid. The most pressing pain point is the message-encryption phase itself; sessions sometimes never initialise or silently fall back to no cipher at all.

Deliverables I expect:
• Diagnose why sessions aren’t being created or restored in time and why ciphertext occasionally downgrades to plaintext.
• Patch or rewrite the relevant pieces (likely around X3DH key pre-keys and Double Ratchet state handling) so every outgoing message is encrypted end-to-end, every time.
• Provide repeatable tests or a small test harness proving that plaintext leaks are impossible under normal use (new user with no keys, broken session, concurrent devices, etc.).
• Document any code changes and configuration tweaks so I can maintain the solution after your fix ships.

Everything is needed ASAP; the sooner we can stop cleartext from leaking, the faster the product can be safe. If you can demonstrate past work with Signal, X3DH or similar E2E stacks (THAT YOU KNOW HOW TO CORRECT CODE ENCRYPT AND DECYRYPT FILES IMAGES VDEOS TEXT FOR APPS), I’m ready to hand you access and get started immediately." (client-provided description)