This event was removed in v385

This event is no longer emitted in the current runtime. Existed from v361 to v385. Shown here for historical reference.

DecryptionFailed

Event Removed v361 → v385 (removed) #3

Emitted when the validator couldn't decrypt an encrypted submission.

Useful for: stakersdevelopersvalidatorsanalytics

The Big Picture

Something went wrong with the cryptography. Maybe you encrypted with the wrong epoch's key, the ciphertext was corrupted, or the format was invalid. The validator couldn't decrypt your submission, so your transaction is lost. The 'reason' field helps diagnose what went wrong.

Why This Matters

If decryption fails, your transaction is gone - the inner contents can't be recovered. This event tells you what went wrong (wrong key? bad format?) so you can fix your client and retry. Always test encryption carefully before submitting real transactions.

Example Scenario

You cached an old NextKey and encrypted with it, but the key epoch expired before your submission was processed. DecryptionFailed fires with id=0x123..., reason='KeyExpired'. Your transaction is lost. Fix: Always fetch fresh NextKey immediately before encrypting.

Common Questions

Can I recover my transaction?: No. If decryption failed, the inner transaction is unrecoverable. This is why testing encryption flow thoroughly before real usage is critical.
What are common failure reasons?: 1) KeyExpired - used wrong epoch's key, 2) ML-KEM decapsulate failed - key/ciphertext mismatch, 3) AEAD decrypt failed - corrupted data, 4) Invalid format - wrong ciphertext structure.
Could the validator be lying about failure?: Technically yes, but it's auditable. False decryption failures would damage validator reputation and could be detected by comparing expected vs actual behavior across many submissions.

Use Cases

Diagnose encryption/submission problems
Track decryption failure rates
Debug MEV-protection client implementations
Audit validator behavior

How to Use This Event

→ Monitor your submission IDs for this failure event
→ Parse reason to fix client-side encryption bugs
→ Alert on elevated decryption failure rates

From Chain Metadata

Decryption failed - validator could not decrypt the submission.

Part of: MEV Shield

Triggers

Emitted by

mark_decryption_failed

Preconditions

Submission existed in Submissions storage
Decryption was attempted by block author
Cryptographic operation failed

Effects

Storage Modified

Submissions

Postconditions

Submission removed from Submissions storage
Failure reason recorded in event
Inner transaction never seen or executed

Side Effects

User's encrypted transaction lost (can't be recovered)
Provides debugging information via reason field

Event Data

#	Name	Type	Description
0	id → submission_id	H256	Identifier of the submission that could not be decrypted
1	reason → failure_reason	BoundedVec	Human-readable reason for the decryption failure

Code Examples

import { ApiPromise, WsProvider } from "@polkadot/api";
import { stringCamelCase } from "@polkadot/util";

const provider = new WsProvider("wss://entrypoint-finney.opentensor.ai:443");
const api = await ApiPromise.create({ provider });

// Subscribe to DecryptionFailed events
api.query.system.events((events) => {
  events
    .filter(({ event }) =>
      event.section === stringCamelCase("MevShield") &&
      event.method === "DecryptionFailed"
    )
    .forEach(({ event }) => {
      console.log("DecryptionFailed:", event.data.toHuman());
    });
});

Runtime Info

View Source

Pallet Index: 30
Event Index: 3
First Version: v361
Removed In: v385

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