IPSec and TLS Flashcards
S/MIME
a security enhancement to the MIME internet email format standard, based on technology from RSA Data Security
MIME
Internet email format
Adds to RFC 822 header (To, From, Subject) fields for to define:
- -body
- -format of body
- -encoding of body
- -content formats (text, image, audio, video) that support multimedia
S/MIME provides support for these 4 additional content-types
Enveloped data
Signed data
Clear-signed data
Signed and enveloped data
Signed data
Digital signature formed by taking the message digest of the content to be signed and then encrypting that with the private key of the signer.
The content plus signature are then encoded using base64 encoding.
Signed data message can only be viewed by a recipient with S/MIME capability
Default algorithm is DSS and SHA-1
Enveloped data
encrypted content of any type and encrypted content encryption keys for one or more recipients
Default algorithm is 3DES and EIGamal (based on Diffie-Hellman)
Clear-signed data
Digital signature of the content is formed
Only the digital signature is encoded using base64 (unlike enveloped data)
Recipients without S/MIME capability can view the message content, although they cannot verify the signature
Default algorithm is DSS and SHA-1
Signed and enveloped data
Signed-only and encrypted-only entities may be nested, so that encrypted data may be signed and signed data or clear-signed data may be encrypted
DomainKeys Identified Mail (DKIM)
Specification for cryptography signing email messages, permitting a signing domain to claim responsibility for a message in the mail stream
Internet Mail Architecture key components
Message User Agent
Mail submission agent
Message transfer agent
Mail delivery agent
Message store
Administrative management domain
Internet email provider
Domain name system
directory lookup service that provides a mapping between the name of a host on the Internet and its numerical address
Spoofing
IP spoofing is a common technique in cyber attacks
Bots spoof the an IP address of a victim web site
Then send DNS queries to DNS servers
The DNS servers respond, sending large amounts of data to the victim
Result: a denial-of-service attack
Goal of IPSec
Prevent spoofing by verifying sources of IP packets
Provide Authentication that is lacking in IPv4
Protect integrity and/or confidentiality of packets
Prevent replaying of old packets
Provide security automatically for upper layer protocols and applications
two operation modes in IPSec
transport mode
security protection is provided to traffic from one end host to another, so, it is an end-to-end.
tunnel mode
security protection is typically provided to traffic from the gateway of a network to the gateway of another network. This is how the so-called virtual private network, or VPN, is implemented.
encapsulated security payload
Encrypt and authenticate each packet
Encryption is applied to packet payload
Authentication is applied to data in the IPSec header as well as the data contained as payload, after encryption is applied
ESP can provide both confidentiality and integrity protection
If the authentication option of ESP is chosen, message integrity code is computed AFTER encryption
To protect the confidentiality and integrity of the whole original IP packet, we can use ESP with authentication option in tunnel mode
Authentication Header (AH)
Authentication is applied to the entire packet, with the mutable fields in the IP header “zeroed out”
If both ESP and AH are applied to a packet, AH follows ESP
In AH, the integrity hash covers the IP header
TLS three higher layer protocols
Handshake protocol
Change cipher spec protocol
Alert protocol
TLS concepts
TLS Connection
TLS Session
TLS Connection
A connection is a transport that provides suitable type of service
Such connections are peer-to-peer
Connections are transient
Every connection is associated with one session
TLS Session
TLS session is an association between a client and a server
Sessions are created by the Handshake Protocol
Sessions define a set of cryptographic security parameters, which can be shared among multiple connections
Sessions are used to avoid negotiation of new security parameters for each connection
SSL Record Protocol services
Confidentiality
–Handshake Protocol defines shared secret key for symmetric encryption of SSL payloads
Message Integrity
–Handshake Protocol defines shared secret key used to form a MAC
Change Cipher Spec Protocol
Consists of single message, which consists of single byte with the value 1
Purpose is to cause the pending state to be copied into the current state, which updates the cipher suite to be used on this connection
Alert Protocol
Used to convey TLS related alerts to the peer entity
Message consists of:
- first byte takes value warning(1) or fatal(2) to convey severity of message
- second byte contains code that indicates the specific alert
Handshake Protocol
Allows server and client to authenticate each other, negotiate an encryption algorithm and MAC algorithm and cryptographic keys
The Parameters:
Version: the highest TLS version understood by the client
Random: a 32-bit timestamp and 28 bytes generated by a secure random number generator
Session ID: a variable-length session identifier
CipherSuite: a list containing the combinations of cryptographic algorithms supported by the client
Compression Method: a list of compression methods supported by the client
Handshake Protocol four phases
Phase 1 used to initiate logical connection between client and server and to establishes security capabilities. Initiated by client with client_hello message and parameters
Phase 2 is server_hello message and parameters
Phase 3 client verifies that server provided valid certificate, check server_hello paramters. Client sends messages back
Phase 4 completes setting up of secure connection
Heartbeat Protocol
Heartbeat is periodic signal generated by hardware or software to indicate normal operation
Heartbeat protocol used to monitor availability of protocol entity
4 SSL/TLS Attack Categories
Attacks on the Handshake Protocol
Attacks on the record and application data protocols
Attacks on the PKI
Other attacks
HTTPS
combination HTTP and SSL to implement secure communications between web browser and web server
Following elements encrypted: URL of requested document Contents of the document Contents of browser forms Cookies sent from browser to server and from server to browser Contents of HTTP header
IP-level security functional areas
Authentication
Confidentiality
Key management
IPSec functions
Combined authentication/encryption function called Encapsulating Security Payload
Key exchange function
