slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Encryption Vulnerabilities PowerPoint Presentation
Download Presentation
Encryption Vulnerabilities

Loading in 2 Seconds...

play fullscreen
1 / 5

Encryption Vulnerabilities - PowerPoint PPT Presentation


  • 66 Views
  • Uploaded on

Encryption Vulnerabilities. Confidentiality. Confidentiality is maintained so long as private keys are secure. Authenticity. Authenticity is possible via public-key encryption by encrypting messages twice: E receiverPubKey ( E senderPrivateKey ( message ) ) …more on this later. Integrity.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Encryption Vulnerabilities' - torie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Encryption Vulnerabilities

Confidentiality

Confidentiality is maintained so long as private keys are secure.

Authenticity

Authenticity is possible via public-key encryption by encrypting messages twice:

EreceiverPubKey( EsenderPrivateKey( message ) )

…more on this later.

Integrity

What prohibits alteration of message parts?

At the very least such alterations should be obviously detected.

Integrity is addressed via …

slide2

ciphertext

plaintext MD

plaintext MD

encryption

algorithm

hash

algorithm

compare

decryption

algorithm

hash

algorithm

Cryptographic Hash Functions

Calculate a hash value / checksum / message digest based upon the message.

The hash algorithm is a one-way function.

Message Encoding

plaintext

Message Decoding

ciphertext

slide3

block1 block2 block3 ... blockN

initial value

H

chain

value

H

chain

value

H

chain

value

message

digest

H

H

Hashing Algorithms

plaintext

chain

value

This H function typically consists of multiple rounds of bitwise logic,

parity calculation, word-sized addition, and bit string partitioning/concatenation.

slide4

Date Block Size Digest Size Compute Steps in H

MD5 1990 512 128 4 rounds of 16

SHA-1 1995 512 160 4 rounds of 20

RIPEMD-160 1996 512 160 4 paired rounds of 16

SHA-512 1995 1024 512 4 rounds of 20

Note that the probability of randomly “guessing” a hash digest of N bits is

1

2N

Best Known Hashing Algorithms

e.g., the odds of calculating a hash match for a 128-bit checksum are 1 in 264 ≈ 2 * 1019

slide5

HMAC

(Hashed Message Authentication Code)

block size

00…0 key

ipad

opad

+

plaintext message

+

block1 block2 block3 ... blockN

hash

algorithm

hash

algorithm

00…0 MD

MD

The HMAC digest

• The HMAC algorithm turns any keyless hashing algorithm into a keyed hash.

• The security of the HMAC algorithm depends upon the chosen hashing algorithm.

ipad is 00110110 repeated to block length.

opad is 01011100 repeated to block length.

Note that HMAC is more

secure than hashing, because

it requires a private key.