You're thinking of darkwallet, https://www.darkwallet.is/ https://www.darkwallet.is/ a browser-based bitcoin wallet that uses coinjoin to obscure transactions

You're thinking of darkwallet, https://www.darkwallet.is/ https://www.darkwallet.is/ a browser-based bitcoin wallet that uses coinjoin to obscure transactions, rather than darkcoin, which is an altcoin that has built in obfuscation based on coinjoin so it happens by default.