Lecture 15: 1st November 2019 Flashcards Preview

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Flashcards in Lecture 15: 1st November 2019 Deck (47)
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What is SSL?

A protocol that enables encrypted communications over a network (the Internet). SSL is at the transport layer, sitting on top of TCP, and provides an application interface for secure and encrypted communications.


What is TLS?

A cryptographic protocol implementing secure, encrypted communications over a network. It is at the transport and session layer and is on top of TCP, again providing an application interface for secure and encrypted communications.


What is the difference between SSL and TLS?

SSL preceded TLS, TLS 1.0 was an upgrade of SSL 3.0. TLS has more modern cipher suites and hash algorithms. SSL has one certificate alert message only vs numerous alert messages in TLS. SSL MAC vs HMAC in TLS. Different handshake proceedure.


How does handshaking work in SSL?

user asks a server for its SSL certificate; the server sends its certificate; user checks if they trust the certificate, if so, messaging the server to open an encrypted SSL session; server replies with a digitally signed ack to start the session.


What is IPSec?

A framework of open standards for ensuring private, secure communications over IP networks through the use of end-to-end cryptographic security services. A suite of protocols that provide data authentication, integrity, and confidentiality.


What is the SSL MAC?

MAC = Message Authentication Code = short piece of information used to authenticate a message and to provide integrity and authenticity assurances on the message.


What is the TLS HMAC?

keyed-hash message authentication code = a specific type of MAC, different than that found in SSL.


What is the difference between the SSL MAC and the TLS HMAC?

HMAC includes encrypting the digest of the hash function used with a key negotiated with the other host. HMAC produces an integrity check value as the MAC does, but uses a hash function to strengthen it. There is also more padding than with TLS.


What are some sources of vulnerabilities or ways to find them?

Precursors: Port Scan, Social Engineering, Reconnaissance, Application Fingerprinting.

Authentication: Impersonation, Eavesdropping, spoofing, session hijacking

Confidentiality: Protocol Flaws, Eavesdropping, wiretap, misdelivery, exposure, traffic flow analysis, cookies.

Integrity: Protocol Flaws, wiretap, falsification of messages, network noise,

DNS attack Availability: Protocol Flaws, Component Failure, DoS, Traffic redirection, ping of death, smurf, syn flood.

Programming Flaws: Buffer overflows, addressing errors, cookies, Java, ActiveX malicious code, viruses, etc.

Mobile Agents: malicious agents, webbots.


Which computers are involved in IPSec protection?

The sender and receiver only


Why are a strong cryptographic key and authentication algorithm both needed with encrypted comms?

A strong cryptographic key with a weak authentication algorithm may allow attacker disruption; weak encryption and strong authentication can allow decryption.


What is the drawback of having both a strong cryptographic key and a strong authentication algorithm?

cost of transmission rate and CPU time


How does handshaking work in TLS?

client hello; sever hello + certificate, ask for client certificate, and key exchange; the client sends certificate, finishes key exchange, verifies server certificate, and choose cipher spec; server confirms cipher spec and checks client certificate.


What are the two modes of use of IPSec?

transport and tunnel mode


What is an AH in IPSec?

Authentication Header: a security mechanism to ensure the authenticity and integrity of packets. It adds an extra header containing the message digest of the whole datagram.


What is an ESP in IPSec?

Encapsulated Security Payload: a security mechanism to ensure the confidentiality, integrity, and authenticity of packet payloads. Adds a header with the digest of a hash of the payload and encrypts the payload.


What are the key features of IPSec?

Collection of standards for end-to-end security on IP networks. IPSec was developed to address the needs for data security, integrity, authentication, and protection for network connections which are connectionless and stateless.

Provides security at the network layer:
-All IP datagrams covered.
- No re-engineering of applications.
- Transparent to upper layers.

Mandatory for IPv6, optional for IPv4.


What is an SPI?

Security Parameters Index = an ESP header that identifies which algorithms and keys are to be used for IPSec processing.


What are the key features of IPSec's transport mode?

When you can connect directly between two IPSec-aware hosts as endpoints. Make host-host (end-to-end) security. IPSec processing at each endpoint. Source and destination addresses are unencrypted.


What are the key features of IPSec's tunnel mode?

For IPsec-unaware hosts, tunnel established by intermediate gateways or host OS. A tunnel is established between IPSec gateways; IP packets are encapsulated inside of IPSec packets which are transferred between the gateways before the original IP packet is sent from the receiving gateway by de-encapsulating the IPSec packet.


What does the CIA acronym stand for?

confidentiality; integrity; authentication


How does the CIA acronym apply to ESP?

- Confidentiality: encrypted inner IP datagram, including original S/D addresses, not visible to intermediate routers.
-Integrity: hash of ESP
- Authentication: PSKs


What is a SA in IPSec?

Security Association = a unidirectional relationship between a sender and receiver. It specifies the processing to be applied to this datagram from this sender to this receiver.

The establishment of shared security attributes between two network entities to support secure communication. An SA may include: cryptographic algorithm and mode; traffic encryption key; parameters for the network data to be passed over the connection.


What is a PSK in IPSec?

Pre-shared Key = a symmetric key used to establish mutual authentication and allow IKE


What does an SPI in IPSec contain?

A Security Parameter Index (SPI) which identifies the Security Association (SA) for the IP packet. The SPI and a sequence number constitute the ESP header.


How does a SA in IPSec work in transport mode?

Transport Mode SA - operates between hosts, the original source and destination IP addresses are readable, the hosts do their own AH encapsulation of their data.

A risk exists because the IPSec header sits within the original IP header. This allows an attacker to make intelligent guesses as to where servers are on a network and begin to build a picture of the network.

Transport mode is when the payload only is encrypted.


How does a SA in IPSec work in tunnel mode?

Tunnel Mode SA - this operates normally between routers/ firewalls or router to host and is used in the VPN environment. These are often called Security Gateways or IPsec Gateways because the Gateways provide AH/ESP services to other hosts.

This SA is more secure because a new IP header unrelated to the hosts using the tunnel is created around the IPsec datagram.

The original IP header is included within the encrypted IPSec datagram and so the addresses of the originating devices are hidden.


What does a SA in IPSec contain?

SA = SPI (Sec Parameter index) + Source address+ Destination address+ security protocol (AH or ESP) + algorithm type +keys + key lifetimes + Initialization Vectors (IVs) + sequence number + anti-replay + (tunnel or transport) mode.


How do SAs work?

Active SAs are held in a database (SAD).

Each entry in the Security Association Database (SAD) must indicate whether the SA lookup makes use of the destination, or destination and source IP addresses in addition to the SPI.

For each inbound IPsec-protected packet, search the SAD such that the entry that matches the “longest” SA identifier is found.

1. Search the SAD for a match on (SPI, destination address, source address); if a SAD entry matches, then process the inbound packet with that entry.

2. Otherwise, search the SAD for a match on (SPI, destination address); if a SAD entry matches, then process the inbound packet with that entry.

3. Otherwise, search the SAD for a match on only (SPI) if the receiver has chosen to maintain a single SPI space for AH and ESP, or on (SPI, protocol) otherwise; if a SAD entry matches, then process the inbound packet with that entry.

4. Otherwise, discard the packet and log an auditable event


How is IPSec security policy defined?

Rules stored in a Security Policy Database (SPD). SPD consulted for each
outbound & inbound packet.

Rules decide if packets should be dropped, passed through, encrypted, or MACed, and which key and algorithm to apply

Fields in IP datagram compared to fields in SPD entries to find a match based on source and destination addresses (ranges of addresses stored in SPD), transport layer protocol, and transport layer port numbers, etc.

A match identifies a Security Association (SA) or a group of SAs (or the need for new SA).