Challenge sub trees and make them ready for payout (#434)

## Description
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## Types of Changes
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- [ ] Hotfix
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- [ ] Fix or Feature

## Fix or Feature
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- [ ] Tech Debt (Code improvements)
- [ ] Bug fix (non-breaking change which fixes an issue)
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- [ ] Dependency upgrade (A change in substrate or any 3rd party crate
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### Migrations and Hooks
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- [ ] Modifies `on_initialize`
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- [ ] Change has been tested locally.
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- [ ] `network-relayer`'s
[events](https://github.com/Cerebellum-Network/network-relayer/blob/dev-cere/shared/substrate/events.go)
have been updated according to the blockchain events if applicable.
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## Checklist for Hotfix
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- [ ] Transaction version has been updated if required.
- [ ] Pull Request to `dev` has been created.
- [ ] Pull Request to `staging` has been created.
- [ ] `network-relayer`'s
[events](https://github.com/Cerebellum-Network/network-relayer/blob/dev-cere/shared/substrate/events.go)
have been updated according to the blockchain events if applicable.
- [ ] All CI checks have been passed successfully

## Checklist for Release
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- [ ] Change has been tested in Qanet.
- [ ] Change has been deployed to Testnet.
- [ ] Change has been tested in Testnet.
- [ ] Changelog has been updated.
- [ ] Crate version has been updated.
- [ ] Spec version has been updated.
- [ ] Transaction version has been updated if required.
- [ ] All CI checks have been passed successfully

Cargo.toml

@@ -30,6 +30,7 @@ resolver = "2"
 
 [workspace.dependencies]
 # 3rd-party dependencies
+base64ct = { version = "1.6.0" }
 blake2 = { version = "0.10.4", default-features = false }
 byte-unit = { version = "4.0.19", default-features = false, features = ["u128"] }
 chrono = { version = "0.4.31", default-features = false }

pallets/ddc-verification/Cargo.toml

@@ -10,6 +10,7 @@ repository.workspace = true
 
 [dependencies]
 array-bytes = { workspace = true }
+base64ct = { workspace = true }
 # 3rd-party dependencies
 codec = { workspace = true }
 # Cere dependencies
@@ -23,6 +24,7 @@ hex = { workspace = true }
 itertools = { workspace = true }
 log = { workspace = true }
 polkadot-ckb-merkle-mountain-range = { workspace = true }
+rand = { workspace = true, features = ["small_rng", "alloc"], default-features = false }
 scale-info = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
@@ -45,6 +47,7 @@ sp-keystore = { workspace = true }
 [features]
 default = ["std"]
 std = [
+  "rand/std",
   "hex/std",
   "polkadot-ckb-merkle-mountain-range/std",
   "codec/std",