feat: [SIW-3727] Implement soft-crypto utilities for hashing and randomBytes generation

[ale-mazz]

Warning

Depends on #48

Short description

Adds native soft-crypto primitives to the React Native bridge — CSPRNG, hashing, and ES256 signature
verification — as drop-in replacements for their node:crypto/Math.random()

List of changes proposed in this pull request

• Android — new SoftCryptoUtils.kt with pure-JCA + BouncyCastle logic; IoReactNativeCryptoModule.kt
  exposes it via thin @ReactMethod wrappers (randomBytes, hashString, hashBytes, verifyES256)
• iOS — new SoftCryptoUtils.swift using CryptoKit and Security framework; IoReactNativeCrypto.swift
  exposes it via @objc methods registered in IoReactNativeCrypto.m (randomBytes, hashString,
  hashBytes, verifyES256)
• Bridge — src/index.tsx exports:
  • generateRandomBytes(size): Promise<Uint8Array> — CSPRNG via SecureRandom (Android) /
    SecRandomCopyBytes (iOS)
  • generateRandomHex(size): Promise<string> — CSPRNG as a lowercase hex string
  • generateRandomString(size): Promise<string> — CSPRNG as an alphanumeric string (a–z, 0–9)
  • digest(data: string | ArrayBuffer, algorithm?: SupportedHashAlgorithm): Promise<Uint8Array> —
    SHA-256/384/512; directly assignable to the Hasher type from @sd-jwt/types
  • verifyES256(data, signatureBase64url, publicKeyJwk): Promise<boolean> — ECDSA P-256/SHA-256 verifier;
    accepts IEEE P1363 signatures (R‖S) via CryptoKit (iOS) and BouncyCastle SHA256withPLAIN-ECDSA (Android)
  • ES256.getVerifier(publicKeyJwk) — returns a Verifier function directly assignable to the Verifier
    type from @sd-jwt/types
• Example app — added Random Bytes and Hash sections to exercise the new functions

How to test

Run the example app on both platforms (yarn android / yarn ios after pod install).

Random Bytes section:

1. generateRandomBytes(32) — tap and verify a 64-character lowercase hex string is displayed; tap
   again and verify it differs (non-deterministic)
2. generateRandomHex(32) — same as above; output is a raw hex string
3. generateRandomString(32) — tap and verify a 32-character alphanumeric string (a–z, 0–9) is
   displayed

Hash section:

1. digest (string) — tap and verify the hex digest of "Hello, world!" matches the known SHA-256
   value (315f5bdb...)
2. digest (ArrayBuffer) — tap and verify the same digest is displayed
3. Both match? — tap and verify the log shows ✓ YES

Repeat on both platforms to confirm consistent output across Android and iOS.

[github-actions]

Jira Pull Request Link

This Pull Request refers to Jira issues:

• SIW-3727

[Copilot]

Pull request overview

This PR adds cross-platform “soft crypto” primitives (salt generation, hashing, ephemeral ECDSA keypairs, sign/verify) implemented natively on Android (JCA/BC) and iOS (CryptoKit), exposes them through the React Native bridge, and provides high-level ES256/ES384/ES512 helpers plus example app UI updates.

Changes:

• Added native soft-crypto implementations and React Native bridge methods for salt/hash/ephemeral ECDSA operations.
• Added JS/TS bridge exports and ES256/ES384/ES512 helper APIs mirroring a WebCrypto-like shape.
• Refactored the example app UI to include a “Soft Crypto” section and improved styling/layout.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
src/index.tsx	Exposes new soft-crypto primitives and ES256/ES384/ES512 helpers via the JS API.
ios/SoftCryptoUtils.swift	Implements salt/hash and ephemeral ECDSA key ops using CryptoKit.
ios/IoReactNativeCrypto.swift	Bridges soft-crypto utilities to React Native promises and adds new iOS error codes.
ios/IoReactNativeCrypto.m	Registers the new iOS bridge methods with React Native.
ios/IoReactNativeCrypto.xcodeproj/project.pbxproj	Adds SoftCryptoUtils.swift to the iOS build.
android/.../SoftCryptoUtils.kt	Implements salt/hash and ephemeral ECDSA key ops using JCA + BC ASN.1 conversion.
android/.../IoReactNativeCryptoModule.kt	Exposes soft-crypto methods through @ReactMethod bridge wrappers and adds new Android error codes.
example/src/App.tsx	Reorganizes UI into sections and adds soft-crypto demo actions.
example/ios/Podfile.lock	Updates lockfile checksum after iOS changes.
example/ios/.../project.pbxproj	Updates Xcode project configuration (notably test target-related entries).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 10 changed files in this pull request and generated 11 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 18 changed files in this pull request and generated 7 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.