Cryptography cs.CR

Today's blockchain is like a music box: the melody (the rules of the game) is embedded in the mechanism, and to change it you have to take the whole thing apart. Every time developers want to change an application's logic, they have to perform a fork, splitting the network into two branches that then compete with each other.

Energy as a signature: the sign of the transferred pulse reveals the secret. This metaphor is the key to a new quantum key distribution protocol that uses energy teleportation instead of state measurement.

When a computer can't handle multiplying two giant tables of numbers, they're sliced into tiny pieces and sent out to dozens of helper servers. For secret data, mathematical tricks are used so the helpers never see the original numbers. Usually, the higher the secrecy, the more servers you need. The authors proposed using a special quantum property — entanglement between the servers.

A quantum computer in the lab resembles an orchestra: lasers play the role of bows, and ions are the strings. To play the desired melody, powerful radio signals are sent to the lasers: they set the rhythm and pitch. But part of this "music" escapes the stage.

A laser that usually produces a steady beam starts to tremble near its threshold, like a string about to sound. This trembling is not a defect but quantum noise: atoms inside the laser emit light randomly, without any external cause.

A cloud service dishes out commands to a drone swarm without any knowledge of their movements. The signals are encrypted, but each maneuver leaves a barely visible trace in the cipher, like ink bleeding through paper from the pressure of a pen. Over time, these ink stains coalesce into a pattern, and the hidden data is no longer a secret.