SecureBitChat/securebit-chat
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Fix cryptographic random bias in getUnbiasedRandomInRange

Browse Source 
Reworked getUnbiasedRandomInRange() to eliminate modulo bias by using
rejection sampling combined with bucket indexing instead of the `%` operator.
Added getUnbiasedRandomFloat() to safely generate unbiased floats for
sizeVariation and sizeMultiplier.
This commit is contained in:
lockbitchat
2025-10-20 00:34:17 -04:00
parent 4233ba3d7e
commit 60e4bb6b8a
3 changed files with 44 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
dist/app-boot.js vendored
View File

@@ -8193,13 +8193,17 @@ var EnhancedSecureWebRTCManager = class _EnhancedSecureWebRTCManager {
this._secureLog("error", "\u274C Failed to initialize enhanced security", { errorType: error.constructor.name });
}
}
// Helper function to generate unbiased random values in a range
// Helper function: unbiased integer in [min, max]
getUnbiasedRandomInRange(min, max) {
if (!Number.isInteger(min) || !Number.isInteger(max)) {
throw new Error("getUnbiasedRandomInRange requires integer min and max");
}
const range = max - min + 1;
if (range <= 0) throw new Error("Invalid range");
const bytesNeeded = Math.ceil(Math.log2(range) / 8);
const bytesNeeded = Math.max(1, Math.ceil(Math.log2(range) / 8));
const maxValue = Math.pow(256, bytesNeeded);
const threshold = maxValue - maxValue % range;
const bucketSize = threshold / range;
let randomValue;
do {
const randomBytes = crypto.getRandomValues(new Uint8Array(bytesNeeded));
@@ -8208,16 +8212,22 @@ var EnhancedSecureWebRTCManager = class _EnhancedSecureWebRTCManager {
randomValue = randomValue << 8 | randomBytes[i];
}
} while (randomValue >= threshold);
return randomValue % range + min;
return min + Math.floor(randomValue / bucketSize);
}
// Generate fingerprint mask for anti-fingerprinting with enhanced randomization
// Helper: unbiased float in [minFloat, maxFloat] with optional precision
getUnbiasedRandomFloat(minFloat, maxFloat, scale = 100) {
const minInt = Math.round(minFloat * scale);
const maxInt = Math.round(maxFloat * scale);
const intVal = this.getUnbiasedRandomInRange(minInt, maxInt);
return intVal / scale;
}
// Generate fingerprint mask
generateFingerprintMask() {
const cryptoRandom = crypto.getRandomValues(new Uint8Array(128));
const mask = {
timingOffset: this.getUnbiasedRandomInRange(0, 1500),
// 0–1500ms
sizeVariation: this.getUnbiasedRandomInRange(75, 125) / 100,
// 0.75–1.25
sizeVariation: this.getUnbiasedRandomFloat(0.75, 1.25),
// float, unbiased
noisePattern: Array.from(crypto.getRandomValues(new Uint8Array(64))),
headerVariations: [
"X-Client-Version",
@@ -8233,8 +8243,8 @@ var EnhancedSecureWebRTCManager = class _EnhancedSecureWebRTCManager {
"X-Private"
],
noiseIntensity: this.getUnbiasedRandomInRange(50, 150),
// 50–150%
sizeMultiplier: this.getUnbiasedRandomInRange(75, 125) / 100,
sizeMultiplier: this.getUnbiasedRandomFloat(0.75, 1.25),
// float, unbiased
timingVariation: this.getUnbiasedRandomInRange(100, 1100)
};
return mask;