Security Concepts

Outline (Security Concepts)

Security Concepts [3]
Browser Security & Privacy [4]
Security 101 [8]
1. Secret-Key Cryptography [2]
2. Public-Key Cryptography [2]
3. Cryptographic Protocols [2]
HTTP over SSL (HTTPS) [5]
Privacy on the Web [3]
Conclusions [1]

Security Concepts D. Mahendran: Security & Privacy

(4) Identification

Identity is required for any non-anonymous communications
- groups can have an identity (facebook members see more than non-members)
- pseudonyms are hidden identities (the real identity is not visible)
- personal identity should be tied to a person itself
Proof of Identity is important for any privileged operation
- signatures and seals are traditional ways
- traditional ways are mostly protected by law (but not really safe)
- more modern ways often include technical methods for Authentication [Authentication (1)]
Client identity on the Web can be bound in three ways:
1. Computer (most of the time identified by an IP Address [Internet Architecture; IP Address (1)])
2. Browser (in the form of a stored cookie [Web Storage; Cookies (1)])
3. User (identified through some authentication method [Authentication (1)])

Security Concepts D. Mahendran: Security & Privacy

(5) Authentication

Authentication is the process of verifying an identity
- the weakest form of authentication is simply trust
- legal consequences can make it more risky to falsify authentication
- technical measures should make it hard to impossible to falsify authentication
Authentication on the Web comes in many different flavors
- implicitly by accessing a server from some IP Address [Internet Architecture; IP Address (1)] range
- presenting a cookie [Web Storage; Cookies (1)] from a previous formal authentication
- presenting a password as a proof of identity
- proving that you are owning additional authentication hardware (often PIN [http://en.wikipedia.org/wiki/Personal_identification_number]-enabled)
Risk and potential damage should justify authentication methods

Security Concepts D. Mahendran: Security & Privacy

(6) Authorization

Authorization is the question of allowing operations
- Identification [Identification (1)] is necessary to identify the initiator
- Authentication [Authentication (1)] is necessary to verify the initiator's identity
- if the initiator is authorized, the operation can be performed
Web pages often are public or restricted access
- public web pages do not require any identification (and thus authentication)
- restricted access Web pages can be group pages (internal company pages)
- personal access is another popular scenario (email, facebook, online banking)
Web servers have well-defined ways of performing authentication [URIs & HTTP; HTTP Authentication (1)]

Browser Security & Privacy

Outline (Browser Security & Privacy)

Security Concepts [3]
Browser Security & Privacy [4]
Security 101 [8]
1. Secret-Key Cryptography [2]
2. Public-Key Cryptography [2]
3. Cryptographic Protocols [2]
HTTP over SSL (HTTPS) [5]
Privacy on the Web [3]
Conclusions [1]

Browser Security & Privacy D. Mahendran: Security & Privacy

(8) Trust and Security on the Web

Web-based applications introduce many risks
- do you trust your browser? (it may not safeguard your information)
- do you trust your computer? (it may have a virus)
- do you trust your network? (it may be monitored on various levels)
- do you trust the server? (it may be a fake phishing [http://en.wikipedia.org/wiki/Phishing] server)
Most of these risks are amplified by the Web's scale
- phishing and spamming only work because the Web makes fraud more effective
Controlling Web access is important for safe browsing
- trusting shared browsers is risky (they may store logins and cache pages)
- trusting the network can be risky (more and more networks are wire-tapped)
- trusting the server is risky (phishing and poor server security)

Browser Security & Privacy D. Mahendran: Security & Privacy

(9) Privacy Options

Browser Security & Privacy D. Mahendran: Security & Privacy

(10) Security Options

Browser Security & Privacy D. Mahendran: Security & Privacy

(11) Encryption Options

Security 101

Outline (Security 101)

Security Concepts [3]
Browser Security & Privacy [4]
Security 101 [8]
1. Secret-Key Cryptography [2]
2. Public-Key Cryptography [2]
3. Cryptographic Protocols [2]
HTTP over SSL (HTTPS) [5]
Privacy on the Web [3]
Conclusions [1]

Security 101 D. Mahendran: Security & Privacy

(13) Cryptography

Cryptography is structured into different layers
- layering is a well-established principle for separation of concerns
Cryptographic primitives implement very basic functionality
- changes and advancements in this area are limited to very specialized researchers
- it is easy to make fatal mistakes which then challenge everything built on top if it
Cryptographic protocols assemble primitives into application-level solutions
- primitives solve very basic security problems (fingerprints, encryption, …)
- protocols combine these into applications (digital signatures, secure communications, …)

Security 101 D. Mahendran: Security & Privacy

(14) One-Way Function

Hashes (or message digests) are well-known in computer science
One-way functions are cryptographically safe hashes
- very hard to find an input producing a given output
- very hard to find two inputs producing the same output (collision)

Secret-Key Cryptography

Outline (Secret-Key Cryptography)

Security Concepts [3]
Browser Security & Privacy [4]
Security 101 [8]
1. Secret-Key Cryptography [2]
2. Public-Key Cryptography [2]
3. Cryptographic Protocols [2]
HTTP over SSL (HTTPS) [5]
Privacy on the Web [3]
Conclusions [1]

Secret-Key Cryptography D. Mahendran: Security & Privacy

(16) Plausible Encryption

Secret-Key is was most people think of when thinking of encryption
- symmetric cryptography is another popular term
One key for encryption and decryption
Revealing the key makes encrypted data openly readable
- there must be a secure channel to transport keys, such as diplomatic pouches [http://en.wikipedia.org/wiki/Diplomatic_bag].
Good for long-term relationships with few partners
- exchange secret keys as part of the initial setup of a relationships
- adding partners requires a secure channel for key exchange
- changing keys requires a secure channel for key exchange
Almost impractical in an environment with many ad-hoc partners

Secret-Key Cryptography D. Mahendran: Security & Privacy

(17) Notice the Arrow

Public-Key Cryptography

Outline (Public-Key Cryptography)

Security Concepts [3]
Browser Security & Privacy [4]
Security 101 [8]
1. Secret-Key Cryptography [2]
2. Public-Key Cryptography [2]
3. Cryptographic Protocols [2]
HTTP over SSL (HTTPS) [5]
Privacy on the Web [3]
Conclusions [1]

Public-Key Cryptography D. Mahendran: Security & Privacy

(19) Implausible Encryption

Public-Key intuitively is hard to accept as a concept
- asymmetric cryptography is another popular term
Key pairs of one public and one secret key
- key generation is the process of generating these key pairs
The public key can be made available to the public
- only the secret key can do the inverse operation of the public key
Good for short-term relationships with many partners
- publish your public key so that it can be used worldwide
- everybody can encrypt data using the public key
- only the owner of the secret can can decrypt the message and read it
Computationally expensive and not good for a large amounts of data

Public-Key Cryptography D. Mahendran: Security & Privacy

(20) No Arrow Here …

Public-Key Cryptography (Encrypting with Secret Key)

Cryptographic Protocols

Outline (Cryptographic Protocols)

Security Concepts [3]
Browser Security & Privacy [4]
Security 101 [8]
1. Secret-Key Cryptography [2]
2. Public-Key Cryptography [2]
3. Cryptographic Protocols [2]
HTTP over SSL (HTTPS) [5]
Privacy on the Web [3]
Conclusions [1]

Cryptographic Protocols D. Mahendran: Security & Privacy

(22) Building Secure Applications

Cryptographic primitives in most cases are not sufficient
- they provide basic functionality for fundamental tasks
- they must by combined to provide solutions for real-world problems
Typical problem #1: How to ensure key authenticity
- with insecure keys, the majority of cryptographic methods is worthless
Typical problem #2: How to communicate securely without shared keys
- many interesting scenarios are based on ad-hoc interactions
- secret-key does not work, public-key needs to verify the peer
Typical problem #3: How to check authenticity and integrity of data
- integrity can be done with checksums, but these could be forged
- authenticity needs a cryptographically secure way of combining identity and data

Cryptographic Protocols D. Mahendran: Security & Privacy

(23) Certificate

Certificates are digital signatures issued by a trusted party
- most digital signatures are created with certified public keys
- this means the digital signature is created based on a digitally signed key
Who can you trust on the Web?
- trust can only start to grow based on initial trust in something
- many systems come with pre-installed trust (root certificates)
- certificates from other issuers will cause browsers to complain [https://katapultmedia.com/]
Certificates (like domain names) are a very easy way to make money
- in theory there are different levels of certificates with different levels of identity checking
- in practice most sites choose the cheapest one that does not give an error message

HTTP over SSL (HTTPS)

Outline (HTTP over SSL (HTTPS))

Security Concepts [3]
Browser Security & Privacy [4]
Security 101 [8]
1. Secret-Key Cryptography [2]
2. Public-Key Cryptography [2]
3. Cryptographic Protocols [2]
HTTP over SSL (HTTPS) [5]
Privacy on the Web [3]
Conclusions [1]