Quantum fingerprinting

Quantum fingerprinting is a proposed technique that uses a quantum computer to generate a string with a similar function to the cryptographic hash function. Alice and Bob hold $n$-bit strings $x$ and $y$. Their goal and a referee's is to obtain the correct value of $f(x,y)\; =\; \backslash begin\{cases\}$

1 & \text{if } x = y, \\

0 & \text{if } x \neq y. \\

\end{cases}. To do this, $2^\{n\}$ quantum states are produced from the O(logn)-qubit state fingerprints and sent to the referee who performs the Swap test to detect if the fingerprints are similar or different with a high probability.

{{cite journal

| author = Harry Buhrman, Richard Cleve, John Watrous, Ronald de Wolf

| title = Quantum Fingerprinting

| journal = Physical Review Letters

| volume = 87

| issue = 16

| year = 2001

| page = 167902

| doi = 10.1103/PhysRevLett.87.167902

| pmid = 11690244

| arxiv = quant-ph/0102001

| bibcode = 2001PhRvL..87p7902B

| s2cid = 1096490

}}

If unconditional guarantees of security are needed, and if it is impractical for the communicating parties to arrange to share a secret that can be used in a Carter–Wegman MAC, this technique might one day be faster than classical techniques given a quantum computer with 5 to 10 qubits. However, these circumstances are very unusual and it is unlikely the technique will ever have a practical application; it is largely of theoretical interest.