Mort Anvari Introduction to Encryption Technology To insert your company logo on this slide From the Insert Menu Select “Picture” Locate your logo file Click OK To resize the logo Click anywhere inside the logo. The boxes that appear outside the logo are known as “resize handles.” Use these to resize the object. If you hold down the shift key before using the resize handles, you will maintain the proportions of the object you wish to resize.

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 Anne wants to send to Bob. The plaintext message compressed to make it smaller and the ciphertext stronger. Plaintext Compression Small Plaintext

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

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

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

12 Example: Encrypted 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

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

14 Example: Encrypted 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

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

16 Example: Encrypted 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 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. Small Plaintext Hash Function Calculated Fingerprint Received Fingerprint  or 

18 Example: Encrypted 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 Compression Small Plaintext