Missed part one? Read How shielded assets thwart phishing attacks to see how transparent ledgers provide attackers with the data needed for whale watching and targeted phishing campaigns.
Privacy is a critical component of security. Over recent months, it has become abundantly clear that there is a direct connection between privacy, protection from financial exposure, and the requirements for bringing businesses on-chain.
Commercial enterprises and everyday users alike cannot operate safely when their transaction histories and treasury balances are exposed to public surveillance and automated data harvesting. True security requires protecting people’s private data, not publishing it on-chain where it can be accessed and exploited.
Here is how Midnight provides security through privacy at multiple levels, utilizing advanced cryptographic architecture to ensure data remains confidential and inaccessible to attackers.
The brute force problem in standard hashing
Many projects attempt to solve privacy with simple hashing, but in a financial context, these simple masks don’t increase security sufficiently against highly motivated or incentivized attackers.
The next line of defense on top of hashing involves random values.
To understand how random values are used to boost security, it helps to understand the limitation of standard hashing in a private environment. Hashing acts as a one-way cryptographic transformation of an input into a unique, fixed-length string called a hash. While it is computationally infeasible with current technology to reverse a hash to find the original data, hashing is currently vulnerable when the range of possible inputs is small or predictable.
If a ledger stores a hashed balance, an attacker can pre-calculate hashes for every common number, such as balances between 1 and 1,000. Comparing these pre-calculated hashes to the values on the public ledger allows the attacker to identify exactly which "hidden" balances belong to which users. This process, known as brute-forcing, can effectively bypass the privacy of a standard hash by turning it into a simple matching game.
To transform this basic privacy into robust security, additional cryptographic layers are required that render this kind of predictive matching computationally infeasible.
Random values and note commitments secure the ledger
Midnight’s architecture eliminates this vulnerability by adding a massive, random secret value to the asset data before hashing occurs. Furthermore, digital notes hold specific values rather than representing a user's total balance. Instead of hashing just a number (e.g., "500"), the protocol hashes the note's value combined with the token type, the owner's key, and this random secret.
This combined input produces a note commitment. Because this secret value is so large and random, a vast number of unique commitments can represent that single value of 500 tokens. An attacker can no longer pre-calculate hashes to find matches because they lack the specific random number, token type, and owner's key used to create the commitment. The ledger appears as a list that reveals no information about the underlying value or the owner.
Commitments and the spending process
The resulting note commitment is what the network records on the blockchain. This commitment acts as a digital seal that "commits" the user to a specific balance and ownership without revealing the details to the public. To the observer, every commitment looks like a random string of characters, regardless of whether it represents one token or one million tokens.
This privacy for the user’s activities translates directly into security. Many attacks rely on the ability to predict user behavior and reconstruct convincing transactions. Keeping that data private secures that potential vector of attack.
But if the ledger hides which note belongs to which user, how does the network verify a transaction and prevent double-spending without exposing the user's history?
On transparent chains, spending an asset requires publicly pointing to an existing balance or unspent output. Doing that on a shielded ledger would destroy privacy by linking past deposits directly to current withdrawals. Midnight resolves this by pairing commitments with two complementary cryptographic tools: zero-knowledge proofs and nullifiers.
- Zero-knowledge proofs: When you prepare to spend a note, you use your secret value and private spending key to generate a zero-knowledge proof. This proof mathematically demonstrates to the network that you possess a valid commitment on the ledger without revealing which commitment it is, what balance it holds, or your private identity.
- Nullifiers: To ensure a note cannot be spent twice, every note commitment has a mathematically linked counterpart called a nullifier. When you spend the note, the transaction publishes this nullifier to an on-chain registry of spent assets. The network verifies that the nullifier has never been published before and marks it as spent. The same commitment always produces the same nullifier, yet an external observer cannot work backward from a nullifier to determine which commitment produced it.
Privacy-enhancing technology adds vital layers of security by starving attackers of the raw data they need to build an exploit in the first place. On a transparent chain, an attacker can monitor public balances, identify high-value wallets, and tailor highly specific phishing lures based on your exact transaction history. On Midnight, the privacy-enhancing technology can protect sensitive data from entering the public domain. When an external attacker cannot scan the chain to see what you hold or who you transact with, they cannot use the ledger to hunt for targets or automate wallet profiling.
Viewing keys
Another line of defense involves viewing keys. Viewing keys separate the authority to inspect incoming data from the authority to spend it. A viewing key decrypts incoming note commitments, allowing the holder to view incoming transfers. It does not reveal outgoing spends, does not display a cumulative balance, and cannot be used to sign transactions or move assets.
Without the viewing key, an external observer scanning the ledger cannot determine a note's contents or its owner.
Privacy is foundational to your security, so be careful how you share your data. Two helpful rules of thumb:
- Connect only to trusted DApps: DApps can request your current balance directly from your wallet. If you connect to a malicious DApp, you might voluntarily expose information to an attacker.
- Never hand your viewing key to untrusted services: Treat your viewing key like a password. If you hand it over to a third-party tool, such as an external scanning or auditing service, they gain a permanent window into your incoming payments. Even though a viewing key cannot move assets, exposing your incoming payment history hands bad actors data they could use to target you.
Protecting your security requires protecting your privacy.
Invisible and invaluable security
Midnight’s privacy-enhancing technology translates directly into improved security, shielding much of the data attackers would use to build customized exploits.
With these protections built into the protocol, users and businesses no longer have to compromise between operating on-chain and safeguarding their sensitive data. Midnight delivers structural defense that is invisible in practice, but invaluable in effect.