spark_rust/signer/traits/
frost.rs

1//! # FROST Nonce Management for Threshold Signatures
2//!
3//! This module defines the trait for managing cryptographic nonces in the FROST
4//! (Flexible Round-Optimized Schnorr Threshold) signature scheme. Proper nonce
5//! generation and management is absolutely critical to the security of threshold
6//! signatures in the Spark wallet.
7//!
8//! In FROST, each signing party generates nonce pairs that:
9//! - Must be unique and unpredictable for each signature
10//! - Must remain secret until the specific phases of the protocol
11//! - Must never be reused across different signing sessions
12//!
13//! This module works in conjunction with the `frost_signing.rs` module, which
14//! implements the actual threshold signing operations.
15
16use frost_secp256k1_tr_unofficial::round1::{SigningCommitments, SigningNonces};
17
18use crate::error::SparkSdkError;
19
20/// Trait for managing cryptographic nonces in FROST threshold signing.
21///
22/// This trait provides methods for generating, storing, and retrieving the nonce
23/// pairs required for FROST threshold signing. Nonce management is a security-critical
24/// component of the FROST protocol, as improper nonce generation or reuse can
25/// lead to private key compromise.
26///
27/// In the FROST protocol flow:
28/// 1. Each participant generates a nonce pair (secret nonces and public commitments)
29/// 2. Participants exchange commitments (not nonces) with each other
30/// 3. When signing occurs, participants reveal their nonces in a controlled manner
31///
32/// The implementation must ensure that:
33/// - Nonces are generated using a cryptographically secure random number generator
34/// - Nonces are never reused across different signing operations
35/// - Nonces are properly stored with their corresponding commitments
36/// - Access to secret nonces is strictly controlled
37pub trait SparkSignerFrost {
38    /// Generates a new (commitments, nonces) pair for a FROST signing round.
39    ///
40    /// This method creates a fresh nonce pair for use in FROST threshold signing
41    /// and stores it securely within the signer's state. The commitments (public part)
42    /// are returned and can be safely shared with other signing participants.
43    ///
44    /// # Returns
45    /// * `Ok(SigningCommitments)` - The public commitments corresponding to the generated nonces
46    /// * `Err(SparkSdkError)` - If nonce generation fails
47    ///
48    /// # Security Considerations
49    /// The implementation must use a secure random number generator to ensure nonces
50    /// are unpredictable. Predictable nonces can lead to private key compromise.
51    fn new_frost_signing_noncepair(&self) -> Result<SigningCommitments, SparkSdkError>;
52
53    /// Exposes the secret nonces corresponding to previously generated commitments.
54    ///
55    /// # Security Warning
56    /// This is a **highly sensitive** operation from a security perspective because
57    /// it reveals confidential material. Improper exposure of nonces can lead to
58    /// private key compromise. Use it **only** when absolutely necessary during the
59    /// FROST signing protocol, and handle the returned nonces with extreme caution.
60    ///
61    /// # Arguments
62    /// * `signing_commitments` - The commitments for which to retrieve the corresponding nonces
63    ///
64    /// # Returns
65    /// * `Ok(SigningNonces)` - The secret nonces corresponding to the provided commitments
66    /// * `Err(SparkSdkError)` - If the nonces cannot be found or another error occurs
67    ///
68    /// # Example
69    /// ```
70    /// # // This is example code and should not be used in production
71    /// # use frost_secp256k1_tr_unofficial::round1::SigningCommitments;
72    /// # fn example(signer: &impl SparkSignerFrost, commitments: SigningCommitments) -> Result<(), SparkSdkError> {
73    /// // This should only happen during the actual signing phase of FROST
74    /// let nonces = signer.sensitive_expose_nonces_from_commitments(&commitments)?;
75    /// // Use nonces immediately for signing and then ensure they're securely erased
76    /// # Ok(())
77    /// # }
78    /// ```
79    fn sensitive_expose_nonces_from_commitments<T>(
80        &self,
81        signing_commitments: &T,
82    ) -> Result<SigningNonces, SparkSdkError>
83    where
84        T: AsRef<[u8]>;
85
86    /// Retrieves or generates nonces for the given commitments.
87    ///
88    /// This method attempts to retrieve the nonces corresponding to the provided
89    /// commitments. If the commitments are not found or are None, it generates
90    /// a new nonce pair and returns the nonces.
91    ///
92    /// # Security Warning
93    /// This method exposes sensitive cryptographic material and should be used
94    /// with the same caution as `sensitive_expose_nonces_from_commitments`.
95    ///
96    /// # Arguments
97    /// * `signing_commitments` - Optional commitments for which to retrieve nonces
98    ///
99    /// # Returns
100    /// * `Ok(SigningNonces)` - The nonces corresponding to the commitments, or newly generated nonces
101    /// * `Err(SparkSdkError)` - If an error occurs during retrieval or generation
102    fn sensitive_create_if_not_found_expose_nonces_from_commitments(
103        &self,
104        signing_commitments: Option<&[u8]>,
105    ) -> Result<SigningNonces, SparkSdkError>;
106}
spark_rust/signer/traits/frost.rs

spark_rust/signer/traits/
frost.rs
