1.4 - Public Key Infrastructure, Encrypting Data, Key Exchange, Encryption Technologies, Obfuscation, Hashing and Digital Signatures, Blockchain Technology, Certificates

Public Key Infrastructure (PKI)

Policies, procedures, hardware, software, people
• Digital certificates: create, distribute, manage, store, revoke
This is a big, big endeavor
• Lots of planning
Also refers to the binding of public keys to people or devices
• The certificate authority
• It's all about trust

Symmetric encryption

A single, shared key
• Encrypt with the key
• Decrypt with the same key
• If it gets out, you'll need another key
Secret key algorithm
• A shared secret
Doesn't scale very well
• Can be challenging to distribute
Very fast to use
• Less overhead than asymmetric encryption
• Often combined with asymmetric encryption

Asymmetric encryption

Public key cryptography
• Two (or more) mathematically related keys
Private key
• Keep this private
Public key
• Anyone can see this key
• Give it away
The private key is the only key that can decrypt data encrypted with the public key
• You can't derive the private key from the public key

The key pair

Asymmetric encryption
• Public Key Cryptography
Key generation
• Build both the public and private key at the same time
• Lots of randomization
• Large prime numbers
• Lots and lots of math
Everyone can have the public key
• Only Alice has the private key

Key escrow

Someone else holds your decryption keys
• Your private keys are in the hands of a 3rd-party
• This may be within your own organization
This can be a legitimate business arrangement
• A business might need access to employee information
• Government agencies may need to decrypt partner data
Controversial?
• Of course
• But may still be required

It's all about the process

Need clear process and procedures
• Keys are incredibly important pieces of information
You must be able to trust your 3rd-party
• Access to the keys is at the control of the 3rd-party
Carefully controlled conditions
• Legal proceedings and court orders

Encrypting stored data

Protect data on storage devices
• SSD, hard drive, USB drive, cloud storage, etc.
• This is data at rest
Full-disk and partition/volume encryption
• BitLocker, FileVault, etc.
File encryption
• EFS (Encrypting File System), third-party utilities

Database encryption

Protecting stored data
• And the transmission of that data
Transparent encryption
• Encrypt all database information with a symmetric key
Record-level encryption
• Encrypt individual columns
• Use separate symmetric keys for each column

Transport encryption

Protect data traversing the network
• You're probably doing this now
Encrypting in the application
• Browsers can communicate using HTTPS
VPN (Virtual Private Network)
• Encrypts all data transmitted over the network, regardless of the application
• Client-based VPN using SSL/TLS
• Site-to-site VPN using IPsec

Encryption algorithms

There are many, many different ways to encrypt data
• The proper "formula" must be used during encryption and decryption
Both sides decide on the algorithm before encrypting the data
• The details are often hidden from the end user
There are advantages and disadvantages between algorithms
• Security level, speed, complexity of implementation, etc.

Cryptographic keys

There's very little that isn't known about the cryptographic process
• The algorithm is usually a known entity
• The only thing you don't know is the key
The key determines the output
• Encrypted data
• Hash value
• Digital signature
Keep your key private!
• It's the only thing protecting your data

Key lengths

Larger keys tend to be more secure
• Prevent brute-force attacks
• Attackers can try every possible key combination
Symmetric encryption
• 128-bit or larger symmetric keys are common
• These numbers get larger and larger as time goes on
Asymmetric encryption
• Complex calculations of prime numbers
• Larger keys than symmetric encryption
• Common to see key lengths of 3,072 bits or larger

Key stretching

A weak key is a weak key
• By itself, it's not very secure
Make a weak key stronger by performing multiple processes
• Hash a password. Hash the hash of the password. And continue…
• Key stretching, key strengthening
Brute force attacks would require reversing each of those hashes
• The attacker has to spend much more time, even though the key is small

Key exchange

A logistical challenge
• How do you share an encryption key across an insecure medium without physically transferring the key?
Out-of-band key exchange
• Don't send the symmetric key over the 'net
• Telephone, courier, in-person, etc.
In-band key exchange
• It's on the network
• Protect the key with additional encryption
• Use asymmetric encryption to deliver a symmetric key

Real-time encryption/decryption

There's a need for fast security
• Without compromising the security part
Share a symmetric session key using asymmetric encryption
• Client encrypts a random (symmetric) key with a server's public key
• The server decrypts this shared key and uses it to encrypt data
• This is the session key
Implement session keys carefully
• Need to be changed often (ephemeral keys)
• Need to be unpredictable

Symmetric key from asymmetric keys

Use public and private key cryptography to create a symmetric key
• Math is powerful

Trusted Platform Module (TPM)

A specification for cryptographic functions
• Cryptography hardware on a device
Cryptographic processor
• Random number generator, key generators
Persistent memory
• Unique keys burned in during manufacturing
Versatile memory
• Storage keys, hardware configuration information
• Securely store BitLocker keys
Password protected
• No dictionary attacks

Hardware Security Module (HSM)

Used in large environments
• Clusters, redundant power
• Securely store thousands of cryptographic keys
High-end cryptographic hardware
• Plug-in card or separate hardware device
Key backup
• Secure storage in hardware
Cryptographic accelerators
• Offload that CPU overhead from other devices

Key management system

Services are everywhere
• On-premises, cloud-based
• Many different keys for many different services
Manage all keys from a centralized manager
• Often provided as third-party software
• Separate the encryption keys from the data
All key management from one console
• Create keys for a specific service or cloud provider (SSL/TLS, SSH, etc.)
• Associate keys with specific users
• Rotate keys on regular intervals
• Log key use and important events

Keeping data private

Our data is located in many different places
• Mobile phones, cloud, laptops, etc.
• The most private data is often physically closest to us
Attackers are always finding new techniques
• It's a race to stay one step ahead
Our data is changing constantly
• How do we keep this data protected?

Secure enclave

A protected area for our secrets
• Often implemented as a hardware processor
• Isolated from the main processor
• Many different technologies and names
Provides extensive security features
• Has its own boot ROM
• Monitors the system boot process
• True random number generator
• Real-time memory encryption
• Root cryptographic keys
• Performs AES encryption in hardware
• And more…

Obfuscation

The process of making something unclear
• It's now much more difficult to understand
But it's not impossible to understand
• If you know how to read it
Hide information in plain sight
• Store payment information without storing a credit card number
Hide information inside of an image
• Steganography

Steganography

Greek for "concealed writing"
• Security through obscurity
Message is invisible
• But it's really there
The covertext
• The container document or file

Common steganography techniques

Network based
• Embed messages in TCP packets
Use an image
• Embed the message in the image itself
Invisible watermarks
• Yellow dots on printers

Other steganography types

Audio steganography
• Modify the digital audio file
• Interlace a secret message within the audio
• Similar technique to image steganography
Video steganography
• A sequence of images
• Use image steganography on a larger scale
• Manage the signal to noise ratio
• Potentially transfer much more information

Tokenization

Replace sensitive data with a non-sensitive placeholder
• SSN 266-12-1112 is now 691-61-8539
Common with credit card processing
• Use a temporary token during payment
• An attacker capturing the card numbers can't use them later
This isn't encryption or hashing
• The original data and token aren't mathematically related
• No encryption overhead

Data masking

Data obfuscation
• Hide some of the original data
Protects PII
• And other sensitive data
May only be hidden from view
• The data may still be intact in storage
• Control the view based on permissions
Many different techniques
• Substituting, shuffling, encrypting, masking out, etc.

Hashes

Represent data as a short string of text
• A message digest, a fingerprint
One-way trip
• Impossible to recover the original message from the digest
• Used to store passwords / confidentiality
Verify a downloaded document is the same as the original
• Integrity
Can be a digital signature
• Authentication, non-repudiation, and integrity

Collision

Hash functions
• Take an input of any size
• Create a fixed size string
• Message digest, checksum
The hash should be unique
• Different inputs should never create the same hash
• If they do, it's a collision
MD5 has a collision problem
• Found in 1996 - Don't use MD5 for anything important

Practical hashing

Verify a downloaded file
• Hashes may be provided on the download site
• Compare the downloaded file hash with the posted hash value
Password storage
• Instead of storing the password, store a salted hash
• Compare hashes during the authentication process
• Nobody ever knows your actual password

Adding some salt

Salt
• Random data added to a password when hashing
Every user gets their own random salt
• The salt is commonly stored with the password
Rainbow tables won't work with salted hashes
• Additional random value added to the original password
This slows things down the brute force process
• It doesn't completely stop the reverse engineering

Salting the hash

Each user gets a different random hash
• The same password creates a different hash

Digital signatures

Prove the message was not changed
• Integrity
Prove the source of the message
• Authentication
Make sure the signature isn't fake
• Non-repudiation
Sign with the private key
• The message doesn't need to be encrypted
• Nobody else can sign this (obviously)
Verify with the public key
• Any change in the message will invalidate the signature

Blockchain

A distributed ledger
• Keep track of transactions
Everyone on the blockchain network maintains the ledger
• Records and replicates to anyone and everyone
Many practical applications
• Payment processing
• Digital identification
• Supply chain monitoring
• Digital voting

Digital certificates

A public key certificate
• Binds a public key with a digital signature
• And other details about the key holder
A digital signature adds trust
• PKI uses Certificate Authorities for additional trust
• Web of Trust adds other users for additional trust
Certificate creation can be built into the OS
• Part of Windows Domain services
• Many 3rd-party options

What's in a digital certificate?

X.509
• Standard format
Certificate details
• Serial number
• Version
• Signature Algorithm
• Issuer
• Name of the cert holder
• Public key
• Extensions
• And more…

Root of trust

Everything associated with IT security requires trust
• A foundational characteristic
How to build trust from something unknown?
• Someone/something trustworthy provides their approval
Refer to the root of trust
• An inherently trusted component
• Hardware, software, firmware, or other component
• Hardware security module (HSM), Secure Enclave, Certificate Authority, etc.

Certificate Authorities

You connect to a random website
• Do you trust it?
Need a good way to trust an unknown entity
• Use a trusted third-party
• An authority
Certificate Authority (CA) has digitally signed the website certificate
• You trust the CA, therefore you trust the website
• Real-time verification

Third-party certificate authorities

Built-in to your browser
• Any browser
Purchase your web site certificate
• It will be trusted by everyone's browser
CA is responsible for vetting the request
• They will confirm the certificate owner
• Additional verification information may be required by the CA

Certificate signing requests

Create a key pair, then send the public key to the CA to be signed
• A certificate signing request (CSR)
The CA validates the request
• Confirms DNS emails and website ownership
CA digitally signs the cert
• Returns to the applicant

Private certificate authorities

You are your own CA
• Build it in-house
• Your devices must trust the internal CA
• Needed for medium-to-large organizations
• Many web servers and privacy requirements
• Implement as part of your overall computing strategy
• Windows Certificate Services, OpenCA

Self-signed certificates

Internal certificates don't need to be signed by a public CA
• Your company is the only one going to use it
• No need to purchase trust for devices that already trust you
Build your own CA
• Issue your own certificates signed by your own CA
Install the CA certificate/trusted chain on all devices
• They'll now trust any certificates signed by your internal CA
• Works exactly like a certificate you purchased

Wildcard certificates

Subject Alternative Name (SAN)
• Extension to an X.509 certificate
• Lists additional identification information
• Allows a certificate to support many different domains
Wildcard domain
• Certificates are based on the name of the server
• A wildcard domain will apply to all server names in a domain
• *.professormesser.com

Key revocation

Certificate Revocation List (CRL)
• Maintained by the Certificate Authority (CA)
• Can contain many revocations in a large file
Many different reasons
• Changes all the time
April 2014 - CVE-2014-0160
• Heartbleed
• OpenSSL flaw put the private key of affected web servers at risk
• OpenSSL was patched, every web server certificate was replaced
• Older certificates were moved to the CRL

OCSP stapling

Online Certificate Status Protocol
• Provides scalability for OCSP checks
The CA is responsible for responding to all client OCSP requests
• This may not scale well
Instead, have the certificate holder verify their own status
• Status information is stored on the certificate holder's server
OCSP status is "stapled" into the SSL/TLS handshake
• Digitally signed by the CA

Getting revocation details to the browser

OCSP (Online Certificate Status Protocol)
• The browser can check certificate revocation
Messages usually sent to an OCSP responder via HTTP
• Easy to support over Internet links
• More efficient than downloading a CRL
Not all browsers/apps support OCSP
• Early Internet Explorer versions did not support OCSP
• Some support OCSP, but don't bother checking