Single Photon Quantum Encryption

1
Single Photon Quantum Encryption

• Rob Grove
• April 25, 2005

2
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions

• Telephone
• Internet
• Courier
• In person

Bob needs to get a secure message to Alice
3
Private Key Cryptography
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions
Private Key Encrypt/Decrypt
Private Key Encrypt/Decrypt
Private Key
Bob
Alice

• Private key encryption uses permutations and
  other reversible mathematical operations to
  encode the message.

Eve
4
Public Key Cryptography
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions
Public Key Encrypt
Encrypted Message
Private Key Decrypt
Bob
Alice
Public Key

• Public key encryption uses prime multiplication
  and other very hard to reverse mathematical
  operations to encode the message.

Eve
5
Quantum bits (Qubits)
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions

• In conventional data transmission every bit has a
  definite value of 0 or 1.
• Linearly polarized atomic particles can be used
  as data bits for quantum data transmission.
• Qubits can change their state when measured.
• Linear polarized photons are natural qubits.
• Qubits are extremely delicate.

6
Polarization of Photons
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions
7
Wave Polarization
Circular Polarization
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions
Linear Polarization
8
Polarizing Filters
Polarized at 45 degrees
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions

• Filters can be used to measure photon
  polarization

• Filters can be used to polarize photons into
  qubits for data transmission

9
Encryption Example
Background
Current Encryption
Quantum Mechanics
Quantum Encryption
Limitations
Predictions
10
Method
2. Alice generates one random sequence and uses
it to filter Bobs data.
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions
Alices Filter
Bob
Bobs Filter
100101010001
110011000100
010111100111
1. Bob generates two random number sequences.
Alice
Subset of Bobs Key
3. Alice tells Bob her filter sequence and Bob
tells her which ones are wrong.
11
Quantum Encryption
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions
Key
Bob
Alice
Introduces gross error gt 25
Eve
12
Shannons Secure Cryptography Equation
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions
The only way this can happen is if a totally
random key of equal length to the message is
XORd with the message.
13
Quantum Encryption Problems
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions

• Restricted to fiber-optics cable
• Greatest distance proven is under 62 miles
• Hardware is expensive
• Individual photons have not been demonstrated
• Data throughput is not very high, 110 kb / s

14
Specific Application Encryption
Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions

• Will not be a substitute for public key
  encryption for most applications
• Will not directly impact 99 of internet users
• Will be a useful tool against massive internet
  attacks on back bone structure
• Will be a solution for line of sight business
  encryption

15
References

• http//www.wsi.tum.de/E24/research/spintronics/spi
  ntronics.htm
• http//www.mycrypto.net/encryption/crypto_algorith
  ms.html
• http//www.tryagain.com/humcivil/qntmencr.htm
• http//www.idquantique.com/files/introduction.pdf
• http//www.cs.jhu.edu/scheideler/courses/600.471_
  S03/lecture_6.pdf
• http//www.cs.dartmouth.edu/jford/crypto.html
• http//www-theory.chem.washington.edu/trstedl/qua
  ntum/quantum.html
• http//scienceworld.wolfram.com/physics/WaveEquati
  on.html
• http//www.wordless.com/CGI/article.asp?ArticleId
  21
• http//www.mtnmath.com/whatrh/node78.html
• http//www.th.physik.uni-frankfurt.de/jr/physpicq
  uant.html
• http//www.trnmag.com/Stories/2002/112702/Fast_qua
  ntum_crypto_demoed_112702.html

Background Current Encryption Quantum
Mechanics Quantum Encryption Limitations Predic
tions