[contracts] Add a bridge contract example demonstrating cross-chain asset transfer risks

[CelestinaBeing]

Context

contracts/bridge/ exists. A bridge contract that demonstrates the most common cross-chain security issues (replay attacks, signature validation) would make an excellent advanced example.

Work

• Implement a simplified Stellar ↔ EVM asset bridge contract
• Demonstrate: replay attack vulnerability (unsigned message reuse), correct nonce-based protection
• Add cross-chain signature validation (Ethereum eth_sign format)
• Write tests showing both the attack and the defense
• sanctifier analyze should flag the replay vulnerability

Acceptance criteria

• Replay attack demonstrated in test
• Nonce-protected version is replay-resistant
• sanctifier analyze detects the replay vulnerability

[GiftedGiftB]

@GiftedGiftB has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue because I can get it done in less than 30 minutes.

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[Turawa2]

@Turawa2 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I can work on the issue perfectly.

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[intelliDean]

@intelliDean has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I'd like to work on this issue

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[DevScoopee]

@DevScoopee has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, I fully understood what is to be done and can deliver. Kindly assign

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[Rampop01]

@Rampop01 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue . I understand the assignment and the requirements, and I’m confident in the approach needed to deliver the best solution. Kindly assign this task to me.

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[drips-wave]

Congratulations, @Rampop01! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Rampop01: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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