Website Security (HTTPS)

ICT@PSU 308-364 Advanced Web Programming 1 of 26

Website Security (Node.js + OpenSSL)

308-364 Advanced Web Programming

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Simplicity is the ultimate sophistication

Leonardo da Vinci


Objectives

• Understanding the basic Cryptography techniques• Symmetric Key Cryptography

• Asymmetric Key Cryptography

• Hybrid Key Cryptography

• Secure the website communication using SSL/TSL• Public Key Infrastructure (PKI)

• Understanding hash functions• MD5• SHA1


Terminology• Code

• Replacement based on words or semantic structures

• Cipher• Replacement based on symbols

• Cryptography• The science of encrypting or hiding secrets.

• Cryptanalysis• The science of decrypting messages or breaking codes and ciphers.

• Cryptology• The combination of the two.

• Plaintext – an unencrypted message• Cyphertext – an encrypted message• Security: a combination of

• Authentication• Access control


Friends and enemies: Alice, Bob, Trudy

securesender

securereceiver

channel data, control messages

data data

Alice Bob

Eve

• well-known in network security world

• Bob, Alice (lovers!) want to communicate “securely”

• Eve (or Trudy, intruder) may intercept, delete, add messages

I love you

I love you I love you


The language of cryptography

plaintext plaintextciphertext

KA

encryptionalgorithm

decryption algorithm

Alice’s encryptionkey

Bob’s decryptionkey

KB

dE@#CFlis^>&

I love you I love you


Three eras of cryptology

• Pre-WWII• Cryptography as a craft

• Widely used, but few provable techniques

• 1940s-1970• Secret key encryption introduced

• Information theory used to characterize security

• 1970-present• Public key systems introduced


Cryptographic Methods

• Symmetric

• Same key for encryption and decryption

• Key distribution problem

• Asymmetric

• Mathematically related key pairs for encryption and decryption

• Public and private keys

• Hybrid

• Combines strengths of both methods

• Asymmetric distributes symmetric key

• Symmetric provides bulk encryption

• Example: SSL negotiates a hybrid method

http://www.tools4noobs.com/online_tools/encrypt/

http://www.tools4noobs.com/online_tools/encrypt/


1. Symmetric Key Cryptography

Encryption

“The quick brown

fox jumps over the

lazy dog”

“AxCv;5bmEseTfid3)fGsm

We#4^,sdgfMwir3:dkJeTsY

8R\s@!q3%”

“The quick brown

fox jumps over the

lazy dog”

Decryption

Plain-text input Plain-text outputCipher-text

Same key(shared secret)


Symmetric Pros and Cons

• Strength:• Simple and really very fast (order of 1000 to 10000 faster than

asymmetric mechanisms)

• Super-fast (and somewhat more secure) if done in hardware (DES, Rijndael)

• Weakness:• Must agree the key beforehand

• Securely pass the key to the other party

• Some algorithms• DES (Modes: ECB, CBC, CFB, OFB, CM), 3DES, AES, IDEA, Blowfish,

RC4, RC5, CAST, SAFER, Twofish


2. Asymmetric Key Cryptography

• AKA. Public Key Cryptography

• Knowledge of the encryption key doesn’t give you knowledge of the decryption key

• Receiver of information generates a pair of keys • Publish the public key in a directory

• Then anyone can send him messages that only she can read


Public Key Encryption

Encryption

“The quick brown

fox jumps over the

lazy dog”

“Py75c%bn&*)9|fDe^bDFa

q#xzjFr@g5=&nmdFg$5kn

vMd’rkvegMs”

“The quick brown

fox jumps over the

lazy dog”

Decryption

Clear-text Input Clear-text OutputCipher-text

Different keys

Recipient’s public key Recipient’s private

key

privatepublic


Public Key Pros and Cons

• Weakness:• Extremely slow

• Susceptible to “known ciphertext” attack

• Problem of trusting public key (see later on PKI)

• Strength• Solves problem of passing the key

• Allows establishment of trust context between parties

• Example algorithms• Diffie-Hellman, RSA, El Gamal, Elliptic Curve Cryptography (ECC)


3. Hybrid Encryption (Real World)

As above, repeated for other

recipients or recovery agents

Digital

Envelope

Other recipient’s or

agent’s public key

(in certificate)

in recovery policy

Launch key for Nuclear missile “RedHeat” is...

Symmetric key

encrypted asymmetrically

(e.g., RSA)

Digital

Envelope

User’s

public key

(in certificate)

RNG

Randomly-

Generated symmetric

“session” key

Symmetric encryption

(e.g. DES)

*#$fjda^j

u539!3t

t389E *&\@

5e%32\^kd


*#$fjda^j

u539!3t

t389E *&\@

5e%32\^kd

Launch keyfor nuclearmissile “RedHeat” is...

Symmetric decryption

(e.g. DES)

Digital

Envelope

Asymmetric decryption of

“session” key (e.g. RSA)

Symmetric

“session” key

Session key must be decrypted

using the recipient’s private keyDigital envelope contains

“session” key encrypted using

recipient’s public key

Recipient’s private key

Hybrid Decryption


Public Key Distribution Problem

• We just solved the problem of symmetric key distribution by using public/private keys

• But…

• Scott creates a keypair (private/public) and quickly tells the world that the public key he published belongs to Bill

• People send confidential stuff to Bill

• Bill does not have the private key to read them…

• Scott reads Bill’s messages

• We require Certificate Authority (CA) and Digital Signature


Creating a Digital Signature

Hash Function

(SHA, MD5)

Jrf843kjfgf*£$&Hdif*7oUs

d*&@:<CHDFHSD(**Py75c%bn&*)9|fDe^bDFaq#xzjFr@

g5=&nmdFg$5knvMd’rkvegMs”

This is a really long

message about Bill’s…

Asymmetric

Encryption

Message or File Digital Signature128 bits Message Digest

Calculate a short message digest from

even a long input using a one-way

message digest function (hash)

Signatory’s private

key

private


Verifying a Digital Signature

Jrf843kjfgf*£$&Hd

if*7oUsd*&@:<CH

DFHSD(**

Py75c%bn&*)

9|fDe^bDFaq

#xzjFr@g5=

&nmdFg$5kn

vMd’rkvegMs”

Asymmetric decryption

(e.g. RSA)

Everyone has access to trusted

public key of the signatory

Signatory’s public

key

Digital Signature

This is a really long

message about Bill’s…

Same hash function

(e.g. MD5, SHA…)

Original Message

Py75c%bn&*)

9|fDe^bDFaq

#xzjFr@g5=

&nmdFg$5kn

vMd’rkvegMs”

? == ?

Are They Same?


What are SSL and TLS?

• SSL – Secure Socket Layer

• TLS – Transport Layer Security

• both provide a secure transport connection between applications (e.g., a web server and a browser)

• SSL was developed by Netscape

• SSL version 3.0 has been implemented in many web browsers (e.g., Netscape Navigator and MS Internet Explorer) and web servers and widely used on the Internet

• SSL v3.0 was specified in an Internet Draft (1996)

• it evolved into TLS specified in RFC 2246

• TLS can be viewed as SSL v3.1


Extended Validation (EV) Certificates

• Certificate request must be approved by a human lawyer at the certificate authority

slide 19


Secure Socket Layer

Client

1. Browser connects to website

Web Server2. Server responds with Certificate and key

CA

3. Client verifies

certificate with CA

Rando

m Key4. Client sends a random key to server

encrypted with the public key

Random

Key

https://www.youtube.com/watch?v=rROgWTfA5qE

https://www.youtube.com/watch?v=rROgWTfA5qE


Notes

• All data encrypted with the servers public key can only be decrypted by the servers private key

• The randomly generated key was:• Randomly Generated by the client• Encrypted with the servers public key

• Only the Server and the Client would know the key, and unless they share it no one else would know.

• Therefore encrypting the Data with the random key secures the data from prying eyes.

• In most applications of SSL/TLS the key type, cipher and hash can be configured based on client and server requirements. It is this that determines the security of your connection, although SSL isn’t without it’s vulnerabilities.


Certificate Authority

• What is Certificate Authorities? • Comodo, Symantec, GoDaddy, GlobalSign, DigiCert

• What are the CA and Public Key algorithm of…• Google

• Facebook

• YouTube

• Instagram• PSU and Science Faculty login page for internet access

https://en.wikipedia.org/wiki/Comodo_Group

https://en.wikipedia.org/wiki/Symantec

https://en.wikipedia.org/wiki/GoDaddy

https://en.wikipedia.org/wiki/GlobalSign

https://en.wikipedia.org/wiki/DigiCert


Hash Functions

• A hash function is any function that can be used to map

digital data of arbitrary size to digital data of fixed size.

• A cryptographic hash function is a hash function which is

considered practically impossible to invert, that is, to recreate the

input data from its hash value alone.

• Applications

• Verifying the integrity of files or messages

• Password verification

• File or data identifier


Hash Function Algorithms

• MD5 hash function widely used (RFC 1321) • computes 128-bit message digest in 4-step process.

• arbitrary 128-bit string x, appears difficult to construct msg m whose MD5 hash is equal to x.

• SHA-1 is also used.• US standard [NIST, FIPS PUB 180-1]

• 160-bit message digest

• http://www.fileformat.info/tool/hash.htm

http://www.fileformat.info/tool/hash.htm


Message-Digest Algorithm 5 (MD5)

• Developed by Ron Rivest in 1991

• Uses 128-bit hash values

• Still widely used in legacy applications although considered insecure

• Various severe vulnerabilities discovered

• Chosen-prefix collisions attacks found by Marc Stevens, Arjen Lenstra and

Benne de Weger

• Start with two arbitrary plaintexts P and Q

• One can compute suffixes S1 and S2 such that P||S1 and Q||S2 collide under MD5 by

making 250 hash evaluations

• Using this approach, a pair of different executable files or PDF documents with the

same MD5 hash can be computed


Secure Hash Algorithm (SHA)

• Developed by NSA and approved as a federal standard by NIST

• SHA-0 and SHA-1 (1993)

• 160-bits

• Considered insecure

• Still found in legacy applications

• Vulnerabilities less severe than those of MD5

• SHA-2 family (2002)

• 256 bits (SHA-256) or 512 bits (SHA-512)

• Still considered secure despite published attack techniques

• Public competition for SHA-3 announced in 2007

Technology

Website Security (HTTPS)