Decrypting Encryption

(for Fun and Profit) Christopher Ward, CISSP, C|CISO

Director of Information Security

Vinson & Elkins, LLP

Just because you’re paranoid

doesn’t mean they’re not out to

get you.

System Centric vs. Data Centric Security

Valuable Data Access Control Lists

Admin Access 2 Factor

Authentication

Firewall

System Centric vs. Data Centric Security

Encryption and Data Centric

Security

Encryption:

o Independent of o operating system

o transmission

o media

o Maintains its own independent ACLs

Protection strength based on algorithms used and key

length

Encryption Types

Hashes

A cryptographic hash function is an algorithm that takes an

arbitrary block of data and returns a fixed-size bit string.

The ideal cryptographic hash function has four main properties:

it is easy to compute the hash value for any given message

it is infeasible to generate a message that has a given hash

it is infeasible to modify a message without changing the hash

it is infeasible to find two different messages with the same

hash.

Common: MD5

SHA1

SHA256

RIPEMD

Encryption Types

Hashes

Password Encryption

Digital Document Fingerprinting

Message Integrity Verification

Encryption Types

Symmetric Encryption

Symmetric-key encryption uses the same cryptographic key (shared key) for both encryption of plaintext and decryption of ciphertext.

Two basic types:

Stream ciphers encrypt the digits/bytes/ characters of a message one at a time.

Block ciphers take a number of bits and encrypt them as a single unit, padding the plaintext so that it is a multiple of the block size.

Encryption Types

Symmetric Encryption

Most common form of encryption

Fast

Control strength by key length and iterations

Common Algorithms: AES

Blowfish

DES / Triple DES

Serpent

Twofish

RC4 (stream)

Encryption Types

Symmetric Encryption

Most common uses:

Local file encryption (MS Word, WinZip, TrueCrypt)

Fixed point-to-point encryption

Device & disk encryption

Asymmetric payload encryption

Symmetric Encryption

Encryption Types

Asymmetric Encryption

Asymmetric-key encryption uses two keys:

1. Public key used for encryption of plaintext

2. Private key used for decryption of ciphertext

Common Algorithms:

RSA

Diffie–Hellman

Digital Signature Standard (DSS)

Elliptic Curve

Encryption Types

Asymmetric Encryption

Secure key distribution

Slower

Associate key with identity

Easier key management

Encryption Types

Asymmetric Encryption

Examples of protocols using asymmetric key algorithms

include:

Internet Key Exchange (X.509 certificates)

Transport Layer Security (TLS)

PGP / OpenPGP / GPG

SSH

Bitcoin

Asymmetric Encryption

Practical Examples

Do you know what I know?

Practical Examples File Sharing with Symmetric Keys

Practical Examples File Sharing with Public Keys

Practical Examples

Digital Signatures

Practical Examples

Cloud “Security”

Perfect Forward Security

Key Length

Asymmetric (RSA) keys

Longer keys = more secure

but longer processing

Key length should be 2048 bits to protect data for about

20 years • 3072 bits for 20+ years

• 4096 bits for lifetime of the universe

• 8192 bits for the uber-paranoid

Key Length

Symmetric Keys

Each bit doubles the key length

256 Bits AES is both fast and secure enough for your lifetime

NSA “Suite B”

http://www.nsa.gov/ia/programs/suiteb_cryptography/index.shtml

Function Use Bits Standard

Hash SHA 256 / 384 FIPS 180-2

Symmetric AES 128 / 256 FIPS 197

Signature ECDSA 256 / 384 FIPS 186-2

Key Exchange ECDH 256 / 384 SP 800-56

Questions