Dark Wallet is a Bitcoin wallet that allows its users to hide their identity during BTC transactions. In other words when you pay something in Bitcoin, your transaction will be grouped with those of other random people who use the same system and will have the effect of producing only one blockchain which will then be used to pay the sellers. This voluntary mix of transactions is encrypted, so it will be difficult for an outside entity spying the service or its users to determine who is sending what to whom.
To anonymize the receiver, Dark Wallet also introduces stealth addresses which, using a cryptographic device, make it possible to mask the final addresses of the transaction by ephemeral and non-traceable addresses.