Cryptography & Security Presented April 16, 2010 By Dave Stycos, Zocalo Data Systems

Security Goals Confidentiality Integrity Availability

Security’s Methods Authentication Access Control Accountability

Discussion Overview Algorithms Protocols Implementations Resources

Classes of Encryption Symmetric Encryption Hashing Random Number Generation Asymmetric Encryption (Public Key)

Symmetric Algorithms Use a secret key to both encrypt and decrypt Are fast Operate on fixed-size blocks (8 or 16 bytes) DES, Triple-DES, AES, RC4, Blowfish

NIST National Institute of Standards and Technology Computer Security Resource Center (CSRC) Federal Information Processing Standards (FIPS) Special Publication 800 (SP-800)

Symmetric Modes Electronic Code Book (ECB) Cipher Block Chaining (CBC) Output Feedback (OFB) Cipher Feedback (CFB) Counter (CTR) More …

Electronic Code Book (ECB)

Encrypted Using ECB Mode

Cipher Block Chaining (CBC)

Encrypted Using CBC Mode

Initialization Vector Not secret Must be unique for each stream or file. Reused IVs reveal patterns in the first blocks of ciphertext.

Common File Headers PDFs %PDF-1.3 JPEG JFIF EXE MZ Therefore, IVs must be unique for each key!

CBC Weaknesses One bad block corrupts the chain Only sequential access Unsuitable for stream ciphers

Block vs. Stream Ciphers Block Ciphers –Operate on data of known, finite size –Files, hard drives Stream Ciphers –Operate on data of unknown, indefinite size –Network flow, media

Cipher Feedback (CFB) Symmetric cipher is a pseudo-random number generator. Plaintext XOR’ed with PRN, not encrypted by cipher.

CFB Weaknesses One bad block corrupts the chain. Only sequential access. Can’t be computed in parallel.

Counter (CTR)

Common Weaknesses Key Secrecy Key Quality

Key Management Locking Is EasyKey Management Is Hard

What Is Key Quality? Computational infeasibility of brute-force attack

What Is Key Quality? Computational infeasibility of brute-force attack DES Key: 56-bits = 72,057,594,037,927,936 keys

What Is Key Quality? Computational infeasibility of brute-force attack DES Key: 56-bits = 72,057,594,037,927,936 keys How secure? Security measured in time. “When” not “if”

Security of 56 Bit DES? 29 PCBs of 64 ASICs = 1856 ASICs! Checked +90b keys/s  9 days Built by EFF in 1998 for $250,000

Advanced Encryption Standard (AES) AES Key: 128-bits = e+38 = 340,282,366,920,938,463,463,374,607,431,770,000,000

Advanced Encryption Standard (AES) AES Key: 128-bits = e+38 = 340,282,366,920,938,463,463,374,607,431,770,000,000 AES Key: 192-bits = e+57 = 6,277,101,735,386,680,763,835,789,423,207,700,000,000, 000,000,000,000,000,000

Advanced Encryption Standard (AES) AES Key: 128-bits = e+38 = 340,282,366,920,938,463,463,374,607,431,770,000,000 AES Key: 192-bits = e+57 = 6,277,101,735,386,680,763,835,789,423,207,700,000,000, 000,000,000,000,000,000 AES Key: 256-bits = e+77 = 115,792,089,237,316,195,423,570,985,008,690,000,000,00 0,000,000,000,000,000,000,000,000,000,000,000,000

Advanced Encryption Standard (AES) AES Key: 128-bits = e+38 = 340,282,366,920,938,463,463,374,607,431,770,000,000 AES Key: 192-bits = e+57 = 6,277,101,735,386,680,763,835,789,423,207,700,000,000, 000,000,000,000,000,000 AES Key: 256-bits = e+77 = 115,792,089,237,316,195,423,570,985,008,690,000,000,00 0,000,000,000,000,000,000,000,000,000,000,000,000 Mass of all visible matter in the universe equiv. 4.0 e+78 hydrogen atoms!

Measuring Key Quality Entropy The likelihood of selecting any single key out of all possible keys.

How to Measure Entropy? 0x F5264

How to Measure Entropy? 0x F P a S s W o R d

How to Measure Entropy? 0x F P a S s W o R d Many keys are derived from passwords. Memorizable pwds = negative effect on entropy.

Entropy of Passwords 64-bits = 1.8 E+19 = 18,446,744,073,709,551,616 keys

Entropy of Passwords 64-bits = 1.8 E+19 = 18,446,744,073,709,551,616 keys 8 chars of lower, upper, numeric = 62^8 = 218,340,105,584,896

Entropy of Passwords 64-bits = 1.8 E+19 = 18,446,744,073,709,551,616 keys 8 chars of lower, upper, numeric = 62^8 = 218,340,105,584,896 ~ 47 bits

Entropy of Passwords 64-bits = 1.8 E+19 = 18,446,744,073,709,551,616 keys 8 chars of lower, upper, numeric = 62^8 = 218,340,105,584,896 ~ 47 bits –Deep Crack Brute Force in 40 minutes!

Entropy of Passwords 64-bits = 1.8 E+19 = 18,446,744,073,709,551,616 keys 8 chars of lower, upper, numeric = 62^8 = 218,340,105,584,896 ~ 47 bits –Deep Crack Brute Force in 40 minutes! 8 chars of alpha-only = 52^8 = 53,459,728,531,456 ~ 45 bits

Entropy of Passwords 64-bits = 1.8 E+19 = 18,446,744,073,709,551,616 keys 8 chars of lower, upper, numeric = 62^8 = 218,340,105,584,896 ~ 47 bits –Deep Crack Brute Force in 40 minutes! 8 chars of alpha-only = 52^8 = 53,459,728,531,456 ~ 45 bits 8 chars, lower-only = 26^8 = 208,827,064,576 ~ 37 bits

Measuring Key Entropy

Dictionary Attacks Reduce entropy by leveraging language patterns

Dictionary Attacks Reduce entropy by leveraging language patterns Merriam-Webster: 250,000 words 250,000 special/scientific 250,000 proper nouns (?) - 1,000 words that are <5 characters = 740,000 ~ 19 bits

Dictionary Attacks Reduce entropy by leveraging language patterns Merriam-Webster: 250,000 words 250,000 special/scientific 250,000 proper nouns (?) - 1,000 words that are <5 characters = 740,000 ~ 19 bits Random use of upper and lower case –Add one bit per char length (max) Random use of upper, lower and numbers –Add ~1.5 bits per char length (max)

Cryptographic Hashing Works like a CRC or checksum Impossible to reverse 128, 160 and 256 bits long Small changes in the plaintext create vast changes in the hash MD5, SHA-1, SHA-256

Hashing Applications Validating data –Verifying download packages (md5sum) Increasing key entropy –2 n hash operations adds n bits of entropy Obscuring passwords

Sending Passwords in the Clear

Obscuring Passwords

Replay Attack

Zero-Knowledge Proof Proving a user knows a piece of data without divulging that piece of data.

Challenge-Response Protocol

NTLM Authentication

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Challenge-Response Protocol Vulnerabilities “Stolen Verifier” Attack No Mutual Authentication

Implementations SSL IPSec Secure Protocols

Recommended Reading “Applied Cryptography” By Bruce Schneier “Practical Cryptography” By Bruce Schneier “Secrets and Lies” By Bruce Schneier “Cryptographic Security Architecture” By Peter Gutmann “Parallelizable Enciphering Mode” By Phillip Rogaway

Organizations Commercial –Schneier.com CryptoGram & blog –RSA, Inc. (rsa.com) PKCS –Internet Engineering Taskforce (ietf.org) RFCs –ANSI, ISO, IEEE, W3C Government –Natl. Inst. of Standards & Tech. (nist.gov) FIPS & SP-800 documents –Natl. Security Agency (NSA)

Happy Crypting! Presentation Created By Dave Stycos April, 2010 © 2010, Zocalo Data Systems, Ltd.