SSLSecure Socket Layer

Srishti Thakkar

Manish Jain

Nehal Dudani

Samip Jain

1

• It is an Internet protocol for secure exchange of information between a web browser and a web server

• It provides

▫ Authentication

▫ Confidentiality

• Developed by Netscape Corporation in 1994

• Currently comes in three versions : 2, 3 and 3.1

2

3

Application Layer

Transport Layer

Internet Layer

Data Link Layer

Physical Layer

SSL Layer

4

X

L5 data

010101010100010101010010

Transmission medium

H4L5 data

H3L4 data

Application

Transport

Internet

Physical

H2L3 data Data Link

Y

L5 data

010101010100010101010010

H4L5 data

H3L4 data

H2L3 data

5

X

L5 data

010101010100010101010010

Transmission medium

H4L5 data

H3L4 data

Application

Transport

Internet

Physical

L5 data SSLSH

H2L3 data Data Link

Y

L5 data

010101010100010101010010

H4L5 data

H3L4 data

L5 data SH

H2L3 data

6

7

1 • Handshake protocol

2 • Record protocol

3 • Change Cipher protocol

4 • Alert protocol

8

Type Length Content

1 byte 3 bytes 1 or more bytes

Message Format

9

Message Type Parameters

Hello request None

Client hello Version, Random number, Session id, Cipher suite,Compression method

Server hello Version, Random number, Session id, Cipher suite,Compression method

Certificate Chain of X.509V3 certificates

Server key exchange Parameters, signature

Certificate request Type, authorities

Server hello done None

Certificate verify Signature

Client key exchange Parameters, signature

Finished Hash value

10

1• Establish security capabilities

2• Server authentication and key exchange

3• Client authentication and key exchange

4• Finish

11

• Used to initiate logical connection and establish security capabilities.

• Consists of two messages

▫ Client hello

▫ Server hello

12

Web Browser

Web Server

Step 1: Client hello

Step 2: Server hello

13

• Identifies highest version of SSL that client can supportVersion

• 32 bit date time field• 28 byte random number

Random

• Variable length session identifier• Can be zero (new session) or non zero (connection exists)

Session id

• Contains list of cryptographic algorithms supported by the clientCipher suite

• Contains list of compression algorithms supported by the client

Compression method

14

• Identifies lower of version suggested by client and highest supported by serverVersion

• Same structure as that in client hello• Random value independent of client’s value

Random

• Uses same value if client sends non zero value• Otherwise creates new session id

Session id

• Contains single cipher suite which server selects from the list sent by clientCipher suite

• Contains single compression algorithm which server selects from the list sent by client

Compression method

15

16

Web Browser

Web ServerStep 2: Server key exchange

Step 3: Certificate request

Step 4: Server hello done

Step 1: Certificate

17

• Server sends its Digital certificate • Helps the to authenticateCertificate

• Sent only if the certificate does not contain enough information to complete the key exchange

Server key exchange

• Sent if the client needs to authenticate itselfCertificate

request

• Sent to indicate that the server is finished its part of the key exchange

• after sending this message the server waits for client response

Server hello done

18

Web Browser

Web Server

Step 1: Certificate

Step 2: Client key exchange

Step 3: Certificate verify

19

• will send a certificate message or a no certificate alertCertificate

• always sent• RSA encrypted pre-master secret

Client key exchange

• sent only if the client sent a certificate• provides client authentication• contains signed hash of all the previous handshake

messages

Certificate verify

20

Master secret

Pre master secret

Client random Server random

Message Digest Algorithm

21

Symmetric Key

Master secret Client random Server random

Message Digest Algorithms

22

Web Browser

Web Server

Step 1: Change cipher specs

Step2 : Finished

Step 3: Change cipher specs

Step 4: Finished

• Provide two services for SSL connections:

Confidentiality: by encrypting application data.

Message Integrity: by computing MAC over the compressed data.

• Can be utilized by some upper-layer protocols of SSL.

24

≤ 214 bytes

(optional; default: null)

25

SSL MAC is computed as:

hash(MAC_write_secret || pad_2 ||

hash(MAC_write_secret || pad_1 || seq_num ||

SSLCompressed.type || SSLCompressed.length ||

SSLCompressed.fragment ) )

26

27

2 byte alert message 1 byte level

Fatal or warning 1 byte

Alert Code

28

Warning or fatal

close_notify(0),

unexpected_message(10),

bad_record_mac(20),

decryption_failed(21),

record_overflow(22),

decompression_failure(30),

handshake_failure(40),

bad_certificate(42),

unsupported_certificate(43),

certificate_revoked(44),

certificate_expired(45),

certificate_unknown(46),

illegal_parameter(47),

unknown_ca(48),

access_denied(49),

decode_error(50),

decrypt_error(51),

export_restriction(60),

protocol_version(70),

insufficient_security(71),

internal_error(80),

user_canceled(90),

no_renegotiation(100),

29

Always fatalunexpected_messagesbad_record_macdecompression_failurehandshake_failureillegal_parameter

30

Remaining alertsclose_notifyno_certificatebad_certificateunsupported_certificatecertificate_revokedcertificate_expiredcertificate_unknown

31

Authentication of server

– How does client know who they are dealing with?

Information integrity– How do we know third party has not altered data en

route?

Bob’s web

siteAlice thinks she is at Bob’s site, but Darth is

spoofing it

Bob’s web

siteAddress information

Change so item shipped to Darth

32

There are several versions of the SSL protocol defined. The latest version, the Transport Layer Security Protocol (TLS), is based on SSL 3.0

SSL Version 1.0

SSL Version 2.0

SSL Version 3.0

TLS Version 1.0

TLS Version 1.0 with SSL Version 3.0

33

www.aiub.edu

34

www.gmail.com

35

www.varsityadmission.com

36

37

https://www.digicert.com/ssl.htm http://www.webopedia.com/TERM/S/SSL.html http://en.wikipedia.org/wiki/Transport_Layer_Security

38