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chore: Add a hint to use offline derivation in the examples #263

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chore: Add a hint to use offline derivation in the examples #263

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4 changes: 4 additions & 0 deletions examples/basic_bls_signing/rust/backend/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -96,6 +96,10 @@ async fn get_my_verification_key() -> VetKeyPublicKey {
context: context(&ic_cdk::api::msg_caller()),
key_id: key_id(),
};

// In production systems it would make sense to use the offline derivation
// support available in ic_vetkeys, eg DerivedPublicKey::derive_sub_key
// since this avoids the cycles and time overhead of a management canister call
Comment on lines +100 to +102
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@fspreiss fspreiss Jan 12, 2026 •
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Here the key is fetched every time anew. Some examples (like examples/basic_timelock_ibe/backend/src/lib.rs) use caching, so they fetch the public key only once. This makes this already much better. We could at least do the caching-based approach in all examples.

Another idea is to detect in which environment we are (mainnet vs pocket-ic) from the key ID: the key ID is passed to the init method and the init-args are defined in the dfx.json.

Ideally we can find a way to automate this (not necessarily in this PR), because this would help developers.

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@fspreiss fspreiss Jan 13, 2026

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Thinking about it more, detecting the environment would be nice, but it's not needed for the time being.

Adding the caching-based approach would already go a long way, and we can extend the hint that the caching could additionally also be done in the frontend, and that frontends could also use the Typescript-based offline key derivation if the caching is not possible (e.g., because there is no fixed context/input).

let result = ic_cdk::management_canister::vetkd_public_key(&request)
.await
.expect("call to vetkd_public_key failed");
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3 changes: 3 additions & 0 deletions examples/basic_ibe/rust/backend/src/lib.rs
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Expand Up @@ -75,6 +75,9 @@ async fn get_ibe_public_key() -> VetKeyPublicKey {
key_id: key_id(),
};

// In production systems it would make sense to use the offline derivation
// support available in ic_vetkeys, eg DerivedPublicKey::derive_sub_key
// since this avoids the cycles and time overhead of a management canister call
let result = ic_cdk::management_canister::vetkd_public_key(&request)
.await
.expect("call to vetkd_public_key failed");
Expand Down
3 changes: 3 additions & 0 deletions examples/basic_timelock_ibe/backend/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,9 @@ async fn get_ibe_public_key() -> VetKeyPublicKey {
key_id: key_id(),
};

// In production systems it would make sense to use the offline derivation
// support available in ic_vetkeys, eg DerivedPublicKey::derive_sub_key
// since this avoids the cycles and time overhead of a management canister call
let result = ic_cdk::management_canister::vetkd_public_key(&request)
.await
.expect("call to vetkd_public_key failed");
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3 changes: 3 additions & 0 deletions examples/encrypted_notes_dapp_vetkd/rust/backend/src/lib.rs
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Expand Up @@ -384,6 +384,9 @@ async fn symmetric_key_verification_key_for_note() -> String {
key_id: key_id(),
};

// In production systems it would make sense to use the offline derivation
// support available in ic_vetkeys, eg DerivedPublicKey::derive_sub_key
// since this avoids the cycles and time overhead of a management canister call
let response: VetKDPublicKeyResult = ic_cdk::management_canister::vetkd_public_key(&request)
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@fspreiss fspreiss Jan 13, 2026

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There is now also the encrypted_chat example, so maybe put the hint also there.

.await
.expect("call to vetkd_public_key failed");
Expand Down