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Version: 1.2.0

@sodot/sodot-react-native-sdk • Docs

@sodot/sodot-react-native-sdk / StatefulBIP340

Class: StatefulBIP340

Class providing the functionality for the BIP340 protocol via the FROST MPC protocol. This class provides a Stateful API meaning that key material will be stored by the SDK on the device.

Example​

// Your server side creates a room for 3 parties using its API_KEY
// Creating a room uuid should always happen on the server side using your API_KEY
const N = 3;
const T = 2;
const bip340 = new StatefulBIP340();
const API_KEY = 'MY_API_KEY';
const keygenRoomUuid = await bip340.createRoom(N, API_KEY);
// All parties call initKeygen to get a keygenId
const keygenId = await bip340.initKeygen('myKeyName');
// All parties receive the keygenIds from all other parties
const keygenIds = [keygenId1, keygenId2];
// All parties join the keygen room
const publicKey = await bip340.keygen(keygenRoomUuid, N, T, 'myKeyName', keygenIds);

// Pick the derivation path of the public key you want to sign for
const derivationPath = new Uint32Array([44,60,0,0,0]);
// Get the public key for the derivation path
const derivedPubkey = await bip340.deriveTweakPubkey('myKeyName', derivationPath);
// To sign a message, create a signing room on the server side, using your API_KEY
const signingRoomUuid = await bip340.createRoom(T, API_KEY);
// The message as a hex string
const message = 'deadbeef';
// 2 parties join the signing room
const signature = await bip340.sign(signingRoomUuid, 'myKeyName', message, derivationPath);
// This signature can now be verified against derivedPubkey

// Refreshing the secret key material
// Your server creates a room for 3 parties
const refreshRoomUuid = await bip340.createRoom(N, API_KEY);
// All parties join the refresh room
await bip340.refresh(refreshedRoomUuid, 'myKeyName', 'myNewKeyName');

// Signing using the new secret key material
// The room is again created by the server
const signingRoomUuid2 = await bip340.createRoom(T, API_KEY);
const message2 = 'deadbeefcafebabe';
const signature2 = await bip340.sign(signingRoomUuid2, 'myNewKeyName', message2, derivationPath);
// This signature can now be verified against derivedPubkey

Constructors​

new StatefulBIP340()​

new StatefulBIP340(hostUrl?): StatefulBIP340

Constructs a new BIP340 instance.

Parameters​

• hostUrl?: string

Returns​

StatefulBIP340

Methods​

createRoom()​

createRoom(numParties, apiKey): Promise<string>

Creates a room for the given number of parties. A room is a one time instance used to perform a single MPC operation(keygen/signing/refresh etc.) between parties

This function should be called in the backend so to not embed the API key in code that is distributed to the users. After the backend calls this function, the other parties can join the room by calling the relevant keygen/signing/refresh/etc. operation.

Parameters​

• numParties: number

The number of parties that will join the room. (an integer in range 1..65_535)

• apiKey: string

An API key is required to create a room

Returns​

Promise<string>

The UUID of the created room.

deletePrivateKeyShareFromDevice()​

deletePrivateKeyShareFromDevice(keyName): Promise<void>

Delete the private key share associated with the given keyName. WARNING: This completely deletes the secret share from the device. This method should only be used either after a refresh operation to delete the old key share or as a way of removing a key from the device. Deletion is irreversible.

Parameters​

• keyName: string

The name of the keypair, this name was used when generating the keypair, the secret share of the keypair will be deleted from this device.

Returns​

Promise<void>

derivePrivateKeyFromXpriv()​

derivePrivateKeyFromXpriv(xpriv, derivationPath?): Promise<string>

Parses an xpriv string according to BIP-32 non-hardened, and returns the derived private key for a given BIP-32 non-hardened derivation path

Parameters​

• xpriv: string

A valid secp256k1 xpriv string.

• derivationPath?: Uint32Array

The BIP-32 non-hardened derivation path to use for computing the private key.

Returns​

Promise<string>

The derived private key of the xpriv.

deriveTweakPubkey()​

deriveTweakPubkey(keyName, derivationPath?, tweak?): Promise<Uint8Array>

Returns the derived public key for keyName for a given BIP-32 non-hardened derivation path

Parameters​

• keyName: string

The name of the keypair, this name was used when generating the keypair.

• derivationPath?: Uint32Array

The BIP-32 non-hardened derivation path to use for computing the public key.

• tweak?: string | Uint8Array

Returns​

Promise<Uint8Array>

The derived public key of the keypair.

exportFullPrivateKey()​

exportFullPrivateKey(roomUuid, keyName, toExportID): Promise<undefined | string>

Combine all secret shares and export the full private key to a single party. Requires a threshold amount of parties to participate.

Parameters​

• roomUuid: string

The UUID of the export room.

• keyName: string

The name of the keypair, the name that was used when generating the keypair.

• toExportID: string

The exportID outputs from exportID() of the party that will receive the private key, this must match between all parties, and the receiving party must participate.

Returns​

Promise<undefined | string>

The party being exported to will receive a string containing the full xpriv, while the rest will receive undefined.

exportID()​

exportID(keyName): Promise<string>

The party that expects to receive the private key needs to call this function before exportFullPrivatekey. It must then transmit the ID to threshold-1 parties, this can be done in an untrusted channel (as if the parties use different keys this will break) Once the parties have the exportID of the party they want to export the private key to, the party and the threshold-1 participants need to call exportFullPrivatekey with that ID.

Parameters​

• keyName: string

The name of the keypair that will be generated later. This name will be used to retrieve a private key associated with the keygenId that is necessary for the keygen operation.

Returns​

Promise<string>

A string that contains a base58 string exportID.

getAllStoredKeyNames()​

getAllStoredKeyNames(): Promise<string[]>

Returns​

Promise<string[]>

A list of all the key names stored on the device.

importPrivateKeyImporter()​

importPrivateKeyImporter(roomUuid, threshold, privateKey, keyName, keygenIds): Promise<Uint8Array>

WARNING: Private key import is an advanced feature of the SDK. We strongly advise consulting with the Sodot team before using it, due to a full private key being imported from a different system. Secret shares generated from imported private keys will always have the risk of the private key having been compromised in the past or in the future in case the private key is not deleted after the import operation.

Importing a full private key, and sharing into a T-of-N sharing, the resultant key shares will be of the exact same public key as the full private key.

This is the method that an importing party (meaning one the party in possesion of the private key) should use for receiving a key share in the new T-of-N quorum.

Parameters​

• roomUuid: string

The UUID of the import room.

• threshold: number

The threshold of the keypair of the new quorum. (an integer in range 1..65_535)

• privateKey: string

The private key to be imported. (a hex string of length 64)

• keyName: string

The name of the keypair. This must be the same name used in initKeygen and will later be used to retrieve the private key share from the secure storage when signing a message.

• keygenIds: string[]

The keygenId outputs from initKeygen(), of all other parties we wish to be part of the new quorum with, keygenIds from all parties must be received through an authenticated communication channel.

Returns​

Promise<Uint8Array>

The public key for the new quorum, same as the pubkey of the imported key.

Example​

const N = 3;
const T = 2;
// A private key is created in some external system.
// const privateKey = "b3ac...0d71"; // hex string with 64 hex chars
// Some time passes...
// Now this party wishes to be part of a new quorum of `2-of-3` sharing of the private key.

// The app server creates a room for N(= 3) parties.
const importRoomUuid = await ecdsa.createRoom(N, API_KEY);
// The other parties must join the import room using the `importPrivateKeyRecipient` method.
const keygenId = await ecdsa.initKeygen('myKeyName'); // This the importing party
// This importing party will send its `keygenId` to all other parties.
// This party will also receive the `keygenId`s of all other parties of the new quorum.
const keygenIds = [keygenId1, keygenId2, keygenId3]; // Note that here we must include our own `keygenId` as well, the order of the ids doesn't matter.
const importPubkey = await ecdsa.importPrivateKeyImporter(importRoomUuid, T, privateKey, 'myKeyName', keygenIds);
// 'myKeyName' can now be used for signing under the T(= 2) threshold with the same public key

importPrivateKeyRecipient()​

importPrivateKeyRecipient(roomUuid, threshold, keyName, keygenIds): Promise<Uint8Array>

WARNING: Private key import is an advanced feature of the SDK. We strongly advise consulting with the Sodot team before using it, due to a full private key being imported from a different system. Secret shares generated from imported private keys will always have the risk of the private key having been compromised in the past or in the future in case the private key is not deleted after the import operation.

Importing a full private key, and sharing into a T-of-N sharing, the resultant key shares will be of the exact same public key as the full private key.

This is the method that a new party (meaning one that does not currently have the private key) should use for receiving a key share in the new T-of-N quorum. The method takes the same input parameters as keygen since for a new party joining the quorum the import operation is very similar to a keygen operation.

Parameters​

• roomUuid: string

The UUID of the import room.

• threshold: number

The threshold of the keypair of the new quorum. (an integer in range 1..65_535)

• keyName: string

The name of the keypair. This must be the same name used in initKeygen and will later be used to retrieve the private key share from the secure storage when signing a message.

• keygenIds: string[]

The keygenId outputs from initKeygen(), of all other parties we wish to be part of the new quorum with, keygenIds from all parties must be received through an authenticated communication channel.

Returns​

Promise<Uint8Array>

The public key for the new quorum, same as the pubkey of the imported key.

Example​

const N = 3;
const T = 2;
// A private key is created in some external system.
// Some time passes...
// Now this party wishes to be part of a new quorum of `2-of-3` sharing of the private key.

// The app server creates a room for N(= 3) parties.
const importRoomUuid = await ecdsa.createRoom(N, API_KEY);
// The party with the private key must join the import room using the `importPrivateKeyImporter` method.
const keygenId = await ecdsa.initKeygen('myKeyName'); // This is a new party
// This new party will send its `keygenId` to all other parties.
// This party will also receive the `keygenId`s of all other parties of the new quorum.
const keygenIds = [keygenId1, keygenId2, keygenId3]; // Note that here we must include our own `keygenId` as well, the order of the ids doesn't matter.
const importPubkey = await ecdsa.importPrivateKeyRecipient(importRoomUuid, T, 'myKeyName', keygenIds);
// 'myKeyName' can now be used for signing under the T(= 2) threshold with the same public key

importPrivateKeyShareData()​

importPrivateKeyShareData(keyName, secretShareHex): Promise<void>

Import a private key share, this function is used to restore a private key share from a backup. The private key share will be stored in the secure storage of the device. (should be a result of calling retrievePrivateKeyShareForBackup)

Parameters​

• keyName: string

• secretShareHex: string

Returns​

Promise<void>

initKeygen()​

initKeygen(keyName): Promise<string>

All parties must call this function before calling keygen. The keyName for the key that will be generated during keygen (and later used for signing as well) is set here. All parties receive a keygenId as an output from this function. This keygenId must be sent through an authenticated communication channel to all other devices we wish to perform keygen with. Once we have the keygenId-s of all parties, then keygen can be called with the same keyName as was given here.

Parameters​

• keyName: string

The name of the keypair that will be generated later. This name will be used to retrieve a private key associated with the keygenId that is necessary for the keygen operation.

Returns​

Promise<string>

A base58 string that represents a keygenId.

keygen()​

keygen(roomUuid, numParties, threshold, keyName, keygenIds): Promise<Uint8Array>

Generate a keypair for the given number of parties and threshold. This function will return the public key of the keypair. The private key is stored in the secure storage of the device and will be used to sign messages.

Parameters​

• roomUuid: string

The UUID of the keygen room.

• numParties: number

The number of parties that will join the keygen room. (an integer in range 1..65_535)

• threshold: number

The threshold of the keypair that will be generated. (an integer in range 1..65_535)

• keyName: string

The name of the keypair. This must be the same name used in initKeygen and will later be used to retrieve the private key share from the secure storage when signing a message.

• keygenIds: string[]

The keygenId outputs from initKeygen of all other parties we wish to perform keygen with, these must have been received through an authenticated communication channel.

Returns​

Promise<Uint8Array>

The public key of the generated keypair.

Example​

// Your server side creates a room for 3 parties using its API_KEY
const N = 5;
const T = 3;
const bip340 = new StatefulBIP340();
const API_KEY = 'MY_API_KEY';
const keygenRoomUuid = await bip340.createRoom(N, API_KEY);

// All parties call initKeygen to get a keygenId
const keygenId = await bip340.initKeygen('myKeyName');
// All parties receive the keygenIds from all other parties
const keygenIds = [keygenId1, keygenId2, keygenId3, keygenId4];
// All parties join the keygen room
const publicKey = await bip340.keygen(keygenRoomUuid, N, T, 'myKeyName', keygenIds);
// publicKey is now distributed between all 5 parties, such that each 3 parties can sign a message.

offlineExportFullPrivateKey()​

offlineExportFullPrivateKey(keygenResults): Promise<string>

Receives as input an array of threshold BIP340KeygenResults and locally computes the full private key (xpriv). The main use case for this function is in an offline recovery setting where keygen results are collected manually and used to recover the full private key on an air-gapped server/device. In order to use key shares exported using retrievePrivateKeyShareForBackup, run new BIP340KeygenResult(undefined!, await bip340.retrievePrivateKeyShareForBackup('myKeyName')) to create a BIP340KeygenResult.

Parameters​

• keygenResults: BIP340KeygenResult[]

An array of threshold BIP340KeygenResults that each contain a secret share of the private key to be locally extracted

Returns​

Promise<string>

A string containing the full xpriv.

pubkeyForKeyName()​

pubkeyForKeyName(keyName): Promise<Uint8Array>

Retrieve the public key associated with the given keyName.

Parameters​

• keyName: string

The name of the keypair, this name was used when generating the keypair.

Returns​

Promise<Uint8Array>

The public key of the keypair.

Deprecated​

It is recommended to use BIP-32 non-hardened derivation instead of the master secret shares when signing.

refresh()​

refresh(roomUuid, keyName, newKeyName): Promise<void>

Used for refreshing the secret material of all parties without altering the public key at all. Takes a keyName and newKeyName as input and stores the fresh key material under newKeyName. Be careful to delete the old keyName share before it is certain that all devices have properly stored the fresh secret material under newKeyName. Note that the new secret materials may only be used with each other, attempting to use older secret materials with newer ones for signing will result in failure. The motivation for using refresh is to enhance security by switching the secret key material frequently, this means that an adversary will need to compromise multiple devices at the same time in order to compromise the private key.

Parameters​

• roomUuid: string

The UUID of the refresh room.

• keyName: string

The name of the key that will be refreshed.

• newKeyName: string

The new name of the key used to store the fresh secret material.

Returns​

Promise<void>

Example​

const N = 5;
const T = 3;
// We now refresh the secret key material of our public key
// Your server creates a room for 3 parties
const refreshRoomUuid = await bip340.createRoom(N, API_KEY);
// All parties now join the refresh room using their current secret key material
await bip340.refresh(refreshRoomUuid, 'myKeyName', 'myNewKeyName');
// 'myNewKeyName' can now be used for signing under the same T threshold, as well as be refreshed again

reshareNewParty()​

reshareNewParty(roomUuid, oldThreshold, newThreshold, keyName, keygenIds): Promise<Uint8Array>

WARNING: Key resharing is an advanced feature of the SDK. We strongly advise consulting with the Sodot team before using it, as incorrect usage might lead to the detriment of the private key security. To use the feature correctly, developers using this feature must make sure that at least n - t + 1 parties of the t-of-n signing quorum delete their current shares before using the resharing of the private key. Also, after resharing, the resharing operation must not be considered complete until such deletion has occurred. Since deleting a share cannot be guaranteed cryptographically, it must be guaranteed by the software architecture (hence, by the developers using the SDK).

Resharing the private key of the t-of-n quorum of signers, the resultant key shares will be of the exact same public key as the previous quorum. Resharing should be used in cases where we aim to modify the current t-of-n quorum with a new quorum with newT-of-newN signers for the same public key.

This is the method that a new party (meaning one that does not currently have a key share) should use for receiving a key share in the new newT-of-newN quorum. The method takes the same input parameters as keygen since for a new party joining the quorum the reshare operation is very similar to a keygen operation. In order to receive the keygenIds of parties that are already a part of the quorum, those parties will need to call exportID() and send the result to the parties in the new quorum.

Parameters​

• roomUuid: string

The UUID of the reshare room.

• oldThreshold: number

The threshold of the existing quorum. (an integer in range 1..65_535)

• newThreshold: number

The threshold of the keypair of the new quorum. (an integer in range 1..65_535)

• keyName: string

The name of the keypair. This must be the same name used in initKeygen and will later be used to retrieve the private key share from the secure storage when signing a message.

• keygenIds: string[]

The keygenId outputs from initKeygen() - for new parties / exportID() - for parties remaining in the quorum, of all other parties we wish to be part of the new quorum with, keygenIds from all parties must be received through an authenticated communication channel.

Returns​

Promise<Uint8Array>

The public key for the new quorum, same as the old pubkey.

Example​

const N = 5;
const T = 3;
const newN = 6;
const newT = 5;
// A signing quorum of `3-of-5` is set up without this party.
// Some time passes...
// Now this party wishes to be part of a new quorum of `5-of-6`.

// The app server creates a room for newN(= 6) parties.
const reshareRoomUuid = await bip340.createRoom(newN, API_KEY);
// At least T(= 3) parties now join the reshare room using the current secret key material (this will be done using `reshareRemainingParty`), all new parties will then join the reshare room using their `initKeygenResult` using `reshareNewParty`.
const keygenId = await bip340.initKeygen('myKeyName'); // This is a new party
// This new party will send its `keygenId` to all other parties.
// This party will also receive the `keygenId`s of all other parties of the new quorum.
const keygenIds = [keygenId1, keygenId2, ..., keygenId6]; // Note that here we must include our own `keygenId` as well, the order of the ids doesn't matter.
const reshareKeygenPubkey = await bip340.reshareNewParty(reshareRoomUuid, T, newT, 'myKeyName', keygenIds);
// 'myKeyName' can now be used for signing under the newT(= 5) threshold with the same public key, as well as be reshared again

reshareRemainingParty()​

reshareRemainingParty(roomUuid, newThreshold, oldKeyName, newKeyName, keygenIds): Promise<Uint8Array>

WARNING: Key resharing is an advanced feature of the SDK. We strongly advise consulting with the Sodot team before using it, as incorrect usage might lead to the detriment of the private key security. To use the feature correctly, developers using this feature must make sure that at least n - t + 1 parties of the t-of-n signing quorum delete their current shares before using the resharing of the private key. Also, after resharing, the resharing operation must not be considered complete until such deletion has occurred. Since deleting a share cannot be guaranteed cryptographically, it must be guaranteed by the software architecture (hence, by the developers using the SDK).

Resharing the private key of the t-of-n quorum of signers, the resultant key shares will be of the exact same public key as the previous quorum. Resharing should be used in cases where we aim to modify the current t-of-n quorum with a new quorum with newT-of-newN signers for the same public key.

This is the method that a remaining party (meaning one that does currently have a key share) should use for receiving a new key share in the new newT-of-newN quorum. The method takes the same input parameters as reshareNewParty except that it will use its existing BIP340KeygenResult instead of a new BIP340InitKeygenResult. In order to receive the keygenIds of parties that are already a part of the quorum, those parties will need to call exportID() and send the result to the parties in the new quorum.

Parameters​

• roomUuid: string

The UUID of the reshare room.

• newThreshold: number

The threshold of the keypair of the new quorum. (an integer in range 1..65_535)

• oldKeyName: string

The name of the keypair. This must be the same name used in the original keygen.

• newKeyName: string

The name of the new keypair for the new quorum.

• keygenIds: string[]

The keygenId outputs from initKeygen() - for new parties / exportID() - for parties remaining in the quorum, of all other parties we wish to be part of the new quorum with, keygenIds from new parties must be received through an authenticated communication channel, keygenIds from remaining parties in the quorum can be sent through any communication channel.

Returns​

Promise<Uint8Array>

The public key for the new quorum, same as the old pubkey.

Example​

const N = 5;
const T = 3;
const newN = 6;
const newT = 5;
// A signing quorum of `3-of-5` is set up with this party.
bip340.keygen(..., 'myOldKeyName', ...);
// Some time passes...
// Now this party wishes to be part of a new quorum of `5-of-6`.

// The app server creates a room for newN(= 6) parties.
const reshareRoomUuid = await bip340.createRoom(newN, API_KEY);
// At least T(= 3) parties now join the reshare room using the current secret key material (this will be done using `reshareRemainingParty`), all new parties will then join the reshare room using their `initKeygenResult` using `reshareNewParty`.
const keygenId = await bip340.exportID('myOldKeyName'); // This is a remaining party
// This remaining party will send its `keygenId` to all other parties (new - via an authenticated channel and remaining - via any channel).
// This party will also receive the `keygenId`s of all other parties of the new quorum (new - via an authenticated channel and remaining - via any channel).
const keygenIds = [keygenId1, keygenId2, ..., keygenId6]; // Note that here we must include our own `keygenId` as well, the order of the ids doesn't matter.
const reshareKeygenPubkey = await bip340.reshareRemainingParty(reshareRoomUuid, newT, 'myOldKeyName', 'myNewKeyName', keygenIds);
// 'myNewKeyName' can now be used for signing under the newT(= 5) threshold with the same public key, as well as be reshared again

retrievePrivateKeyShareForBackup()​

retrievePrivateKeyShareForBackup(keyName): Promise<string>

Retrieve the private key share associated with the given keyName. The returned value is a hex string that encodes the key material. Notice: This value must be kept secret! In case you wish to use the offlineExportFullPrivateKey method that requires an BIP340KeygenResult as input, this may be constructed by running: new BIP340KeygenResult(undefined!, await bip340.retrievePrivateKeyShareForBackup('myKeyName')).

Parameters​

• keyName: string

The name of the keypair, this name was used when generating the keypair.

Returns​

Promise<string>

The private key share of the keypair.

sign()​

sign(roomUuid, keyName, msg, derivationPath?, tweak?): Promise<Uint8Array>

Sign a message with the secret share associated with the given keyName. The secret share is stored in the secure storage of the device. Notice that unlike ECDSA, in BIP340 there's no need to hash the message before signing it.
This supports BIP-341 Taproot tweaking by supplying the T value from the BIP-341 Taproot specification(https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#script-validation-rules):
Let t = hash_<TapTweak>(p || km).
If t ≥ 0xFFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE BAAEDCE6 AF48A03B BFD25E8C D0364141 (order of secp256k1), fail.
Let Q = P + int(t)G.

Parameters​

• roomUuid: string

The UUID of the signing room.

• keyName: string

The name of the keypair, this name was used when generating the keypair.

• msg: string | Uint8Array

The message to be signed. Either as a Uint8Array or as a hex string.

• derivationPath?: Uint32Array

The BIP-32 non-hardened derivation path to use for signing msg.

• tweak?: string | Uint8Array

The tweak to be used for signing. Must be 32 bytes long, either as a Uint8Array or as a hex string.

Returns​

Promise<Uint8Array>

The signature of the message, this signature can be verified using the public key of the keypair.

Example​

// To sign a message, create a signing room on the server side, using your API_KEY
const N = 5;
const T = 3;
const bip340 = new StatefulBIP340();
const API_KEY = 'MY_API_KEY';
const signingRoomUuid = await bip340.createRoom(T, API_KEY);

// Pick the derivation path of the public key you want to sign for
const derivationPath = new Uint32Array([44,60,0,0,0]);
// Get the public key for the derivation path
const derivedPubkey = await bip340.deriveTweakPubkey('myKeyName', derivationPath);
// The message as a hex string
const message = 'deadbeef';
// 3 parties join the signing room
const signature = await ecdsa.sign(signingRoomUuid, 'myKeyName', message, derivationPath);
// This signature can now be verified against derivedPubkey