Ashigaru announcement: https://ashigaru.rs/news/announcement-whirlpool/https://i.ibb.co/Q7G2rDBr/rsa.pngBackground: Nothingmuch had reported a vulnerability in whirlpool in December 2024:
https://groups.google.com/g/bitcoindev/c/CbfbEGozG7c/m/w2B-RRdUCQAJThis allows a malicious coordinator to link inputs and outputs by providing each input with a unique RSA public key. Since the unblinded signatures are
possibly made by different keys, the server can learn the mapping from inputs to outputs.
The blind signing process requires a server or coordinator to share the public key. The highlighted text in the announcement is misleading. I looked at the code in
Whirlpool-Client and
Whirlpool-Server and found that the vulnerability is not fixed.
// generate a secret bordereau. keep it private and register INPUT with blindedBordereau
// bordereau will be provided with unblindedSignedBordereau to register POSTMIX with another
// identity
this.bordereau = ClientUtils.generateBordereau();
byte[] publicKey = WhirlpoolProtocol.decodeBytes(confirmInputMixStatusNotification.publicKey64);
RSAKeyParameters serverPublicKey = ClientUtils.publicKeyUnserialize(publicKey);
this.blindingParams = clientCryptoService.computeBlindingParams(serverPublicKey);
String mixId = confirmInputMixStatusNotification.mixId;
String blindedBordereau64 =
WhirlpoolProtocol.encodeBytes(clientCryptoService.blind(bordereau, blindingParams));
String userHash = premixHandler.computeUserHash(mixId);
ConfirmInputRequest confirmInputRequest =
new ConfirmInputRequest(mixId, blindedBordereau64, userHash);
confirmedInput = true;
return confirmInputRequest;
}
http://ashicodepbnpvslzsl2bz7l2pwrjvajgumgac423pp3y2deprbnzz7id.onion/Ashigaru/Ashigaru-Whirlpool-Client/src/commit/a64bd8b4e0ee8a4cfab03da4565f166d07caa7ec/src/main/java/com/samourai/whirlpool/client/mix/MixProcess.java
// register confirming input
String publicKey64 = WhirlpoolProtocol.encodeBytes(mix.getPublicKey());
ConfirmInputMixStatusNotification confirmInputMixStatusNotification =
new ConfirmInputMixStatusNotification(mix.getMixId(), publicKey64);
mix.registerConfirmingInput(registeredInput);
http://ashicodepbnpvslzsl2bz7l2pwrjvajgumgac423pp3y2deprbnzz7id.onion/Ashigaru/Ashigaru-Whirlpool-Server/src/branch/main/src/main/java/com/samourai/whirlpool/server/services/MixService.javaConclusion: Users should not trust this centralized coordinator and do their own research before paying 5% coordinator fees.
