1. Introduction to Encryption Technology
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Introduction to Encryption Technology
Mort Anvari

2. Encryption
What is it?
- The conversion of data into a form that cannot be easily understood by unauthorized people
- The opposite is decryption, that is, changing the difficult to read form back into the original
- It’s usually software, but can be hardware

3. Cryptography - What does it do for me? - Symmetric Encryption
- Asymmetric Encryption
- One Way Hash
- Example: An Encrypted

4. What does it do for me?
Confidentiality: The data can only be read by the intended recipients
Non-Repudiation: The data cannot be forged. If data is “signed” by a person, the data could only have come from them. No more “I didn’t send that!”
Data Integrity: The data cannot be modified without detection

5. Symmetric Encryption - Data is encrypted and decrypted
with the same key
- Fast
- Key must be kept secret
- Key must be sent Out of Band
- DES and IDEA are symmetric

6. Asymmetric Encryption
- Uses 2 keys
- Data encrypted with one key can
only be decrypted with the other
- Public key is shared with all
- Public key can be sent In Band
- Private key must be kept secret
- RSA is asymmetric

7. One Way Hash - A “fingerprint” of data
- Any size data = same size hash
- Tiny changes in data produce
a very different hash

8. Example: Encrypted E-Mail
Anne wants to send to Bob. The plaintext message compressed to make it smaller and the ciphertext stronger.
Plaintext
Small
Plaintext
Compression

9. Example: Encrypted E-Mail
The plaintext message is run through a hash algorithm to generate a “fingerprint”.
Small
Plaintext
Hash Function
Fingerprint

10. Example: Encrypted E-Mail
The fingerprint is encrypted using Anne’s private key. This makes it into a digital signature. It is then appended to the plaintext.
Small
Plaintext
Anne’s Private
Key
Fingerprint
Signature

11. Example: Encrypted E-Mail
A Random key is generated and the is symmetrically encrypted using that.
Small
Plaintext
Ciphertext
Encrypted
with
Random
Key
Random Key
Signature

12. Example: Encrypted E-Mail
The Random Key is Encrypted using Bob’s public key. The result is called a “Strong Box”. Remember that only Bob can read the contents of the Box.
Bob’s Public
Key
Random Key
A Box for Bob
Random Key

13. Example: Encrypted E-Mail
The Box is attached to the ciphertext and they are sent over to Bob.
Random Key
A Box for Bob
Internet
To Bob
Ciphertext
Encrypted
with
Random
Key

14. Example: Encrypted E-Mail
Bob decrypts his Strong Box to get the Random Key. Only Bob’s private key can open the Box which was encrypted with his public key.
Bob’s Private
Key
Random Key
A Box for Bob
Random Key

15. Example: Encrypted E-Mail
Bob decrypts the ciphertext using the random key which he got from his Strong Box.
Ciphertext
Encrypted
with
Random
Key
Small
Plaintext
Signature
Random Key

16. Example: Encrypted E-Mail
Bob decrypts Anne’s signature using her public key. Since only Anne could have encrypted it with her private key, Bob knows the message had to come from her.
Anne’s Public
Key
Signature
Fingerprint

17. Example: Encrypted E-Mail
Bob runs the unencrypted message through the hash function. If this fingerprint is the same as the one from the signature, the message was not changed in transit.
Calculated
Fingerprint
Small
Plaintext
Hash Function
 or 
Received
Fingerprint

18. Example: Encrypted E-Mail
Finally, the message is uncompressed. Bob can read the message knowing for certain that it’s from Anne, it’s what Anne wrote and only the two of them could have read it.
Plaintext
Small
Plaintext
Compression