sBTC Signers

Overview

The sBTC Signers contract (sbtc-bootstrap-signers.clar) manages the signer set for the sBTC system. It handles rotation of signer keys and provides utilities for generating multisig addresses.

Constants

• key-size: The required length of public keys (33 bytes).

Error Constants

• ERR_KEY_SIZE_PREFIX: Prefix for key size errors in batch processing.

• ERR_KEY_SIZE (u200): Indicates that a provided key is not the correct length.

• ERR_INVALID_CALLER (u201): Signifies that the function caller is not the current signer principal.

• ERR_SIGNATURE_THRESHOLD (u202): Indicates an invalid signature threshold (must be >50% and ≤100% of total signer keys).

Public Functions

rotate-keys-wrapper

Rotates the keys of the signers. Called when the signer set is updated.

• Parameters:

  • new-keys: (list 128 (buff 33)) - List of new signer public keys

  • new-aggregate-pubkey: (buff 33) - New aggregate public key

  • new-signature-threshold: uint - New signature threshold

• Returns: (response (buff 33) uint)

Function flow:

1

Validate signature threshold

Ensure the new signature threshold is valid (must be >50% and ≤100% of total signer keys).

2

Verify caller

Verify that the caller is the current signer principal.

3

Validate keys

Check the length of each new key and the aggregate public key (must be 33 bytes).

4

Update registry

Call the sBTC Registry contract to update the keys and address.

Read-only Functions

pubkeys-to-spend-script

Generates the p2sh redeem script for a multisig.

• Parameters:

  • pubkeys: (list 128 (buff 33)) - List of public keys

  • m: uint - Number of required signatures

• Returns: (buff 1024) - The p2sh redeem script

pubkeys-to-hash

Computes the hash160 of the p2sh redeem script.

• Parameters:

  • pubkeys: (list 128 (buff 33)) - List of public keys

  • m: uint - Number of required signatures

• Returns: (buff 20) - The hash160 of the redeem script

pubkeys-to-principal

Generates a principal (Stacks address) from a set of pubkeys and an m-of-n threshold.

• Parameters:

  • pubkeys: (list 128 (buff 33)) - List of public keys

  • m: uint - Number of required signatures

• Returns: principal - The generated Stacks address

pubkeys-to-bytes

Concatenates a list of pubkeys into a buffer with length prefixes.

• Parameters:

  • pubkeys: (list 128 (buff 33)) - List of public keys

• Returns: (buff 510) - Concatenated pubkeys with length prefixes

concat-pubkeys-fold

Concatenates a pubkey buffer with a length prefix.

• Parameters:

  • pubkey: (buff 33) - A single public key

  • iterator: (buff 510) - Accumulator for concatenation

• Returns: (buff 510) - Updated concatenated buffer

bytes-len

Returns the length of a byte buffer as a single byte.

• Parameters:

  • bytes: (buff 33) - Input byte buffer

• Returns: (buff 1) - Length as a single byte

uint-to-byte

Converts a uint to a single byte.

• Parameters:

  • n: uint - Input number

• Returns: (buff 1) - Number as a single byte

Private Functions

signer-key-length-check

Checks that the length of each key is exactly 33 bytes.

• Parameters:

  • current-key: (buff 33) - Public key to check

  • helper-response: (response uint uint) - Accumulator for error handling

• Returns: (response uint uint) - Updated accumulator or error

Constants

BUFF_TO_BYTE

A constant list mapping uint values (0-255) to their corresponding byte representations.

Interactions with Other Contracts

• .sbtc-registry: Calls get-current-signer-data and rotate-keys to manage signer data.

Security Considerations

• Access Control: Only the current signer principal can call the key rotation function.

• Key Validation: Ensures all provided keys are the correct length.

• Signature Threshold: Enforces a minimum threshold of over 50% of signers and a maximum of 100%.

• Multisig Generation: Provides utilities for secure generation of multisig addresses.