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COMP 208/214/215/216 – Lecture 10. Implementation Issues Security. Database and system Security. Authentication Privacy Integrity Audits and control. Authentication. Commonly based on shared secret Passwords are typically Stored in hashed form

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comp 208 214 215 216 lecture 10

COMP 208/214/215/216 – Lecture 10

Implementation

Issues Security

database and system security
Database and system Security

Authentication

Privacy

Integrity

Audits and control

authentication
Authentication
  • Commonly based on shared secret
  • Passwords are typically
    • Stored in hashed form
    • Used as part of challenge handshake response
    • Should be encrypted before transmitting over the network
password hashing
Password hashing
  • One way function
  • Hash(“secret”)= A13FCB34DF
  • Now the password cannot be read plain from dbase table
  • Salt, helps to protect against pre-computed “rainbow” table, (salt is random bits stored with hash)
  • Rainbow table
    • “cat” ABCEF
    • “fred” 24ABFC
    • “password” 4BAF12
  • Now to attack a particular hash seen on the network one would need to use all different salt combinations
ssl tls https
SSL/TLS/https

SSL

Secure sockets layer, developed by Netscape for secure connection between browsers and web servers

TLS

IETF standard, based on SSL

https

This means http (hyper text transfer protocol transfer securely over TLS)

asymmetric key

Different Keys used for

Encryption and Decryption

Plaintext

Hi Mum

Hi Mum

Plaintext

Key 123

Key ABC

Asymmetric Key

Hi Mum

Hi Mum

Hi Mum

Hi Mum

Hi Mum

Hi Mum

Encryption

Hi Mum

Decryption

Hi Mum

Hi Mum

Hi Mum

GH BVC

Hi Mum

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

H BVC

GH BVC

GH BVC

GH BVC

GH BVC

GH BVC

Hi Mum

Cipher text

Internet Security

digital signature
Digital Signature
  • Example Signature

Internet Security

slide8

Digital Signature

  • Transmission Operation

I would like

to transfer

$1,000,000

Thank you.

I would like

to transfer

$1,000,000

Thank you.

<sig>34E02B2BC8

D746A21B4285C87

E64BA29<sig>

Hash

Function

Digital

signature

Hash Result

E12D4378BA980C1214390

Signing

Function

Sender’s

private key

Internet Security

slide9

Sender’s

public key

Digital Signature

Reception Operation

I would like

to transfer

$1,000,000

Thank you.

<sig>34E02B2BC8

D746A21B4285C87

E64BA29<sig>

Decrypt

Hash Result

E12D4378BA980C1214390

Hash values

the same?

Hash

Function

accept

reject

Internet Security

slide10

Secure Hash Functions

  • h = H(M)
  • Where h = hash value H = hash function M = message
  • Special properties of hash function
  • Different h value for different messages (random distribution)
  • Impossible (very difficult to generate message with given hash value)
  • Very difficult to generate two messages with same hash value i.e. two message M1, M2 where H(M1)=H(M2)

Internet Security

pki public key infrastructure
PKI Public Key Infrastructure
  • Services defined
    • Key/identity binding
    • Key distribution
    • Key integrity
    • Key revocation

Internet Security

pki public key infrastructure1
PKI Public Key Infrastructure

When you connect to web server, using TLS

Web server sends certificate containing

Organisation’s identity

Organisation’s public key

Digital Signature of certification authority

The certificate is validated and then the public key and the private key held at the server is used to

Authenticate the server

Help establish encryption keys between client and server

limitations of https
Limitations of https
  • Only secures data transmission over the Internet, so is just secure transport
  • Does not
    • Secure data in database
    • Provide user authentication
    • Provide security for relayed messages (example for email security)
database encryption options
Database Encryption options
  • Database encryption functions (backend)
    • e.g. MySQL AES_Encrypt
    • Drawbacks… technology specific, change dbase needs re-write
    • Puts extra load on database server
    • Needs secure connections between middleware and backend
  • Middleware encryption (application layer)
    • Easier to port
    • Easier to integrate hardware support for encryption
  • Client side
    • True end to end security
    • Relies on client side key management which is hard to keep secure, v.complex
    • Clients have to be attacked 1 by 1 makes large scale attacks difficult
authentication and authorization
Authentication and authorization
  • Authentication
    • Who are you?
  • Authorization
    • What can you do?
authentication1
Authentication
  • Challenge handshake response
    • Server sends long random number as challenge (nonce)
    • Client responds with nonce encrypted with private key
  • Commonly used in
    • ISP access as part of PPP
authorization
Authorization
  • Run all code through standard API
  • For each user/table have
    • Read/write/insert/delete permissions
  • Can be done at
    • MySQL level (poor granularity, need different MySQL creds. For each user role)
    • Application layer (better flexibility, more coding)
security policy
Security policy
  • Gives the organization
    • A fixed set of rules to secure
      • Passwords, data base access
      • Backups and data integrity
  • Policy
    • Can be analysed and amended to look for weaknesses
    • Guards against adhoc security decisions
security policy examples
Security policy examples
  • Password strength
  • Procedures for password retrieval (email, post or phone)
  • Media
    • Document, USB stick shredding and destruction
    • Removal from site
    • Bringing on to site
  • Backups
    • Encryption
  • Firewall
    • Configuration policy
bell lapadula security model
Bell–LaPadula security model
  • Each user is given security clearance (top secret, secret, public)
    • All documents they develop are automatically set at that clearance
  • Each user can
    • Must not read any document above their clearance (no read up)
    • Must not write any document below their clearance (no write down)
  • Trusted subjects
    • Are allowed to write down, to lower the clearance of secured information
summary
Summary
  • To secure your system you need to
    • Secure the network transport
    • Secure all persistent data
    • Have a proper security policy
    • Protect against physical failure
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