crypto bro rigby. history
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Crypto
Bro Rigby
History
http://en.wikipedia.org/wiki/Cryptography#History_of_cryptography_and_cryptanalysis
Terms
• Plaintext• Encryption• Cipher• Cipher text• Cryptography• Cryptographers
Terms
• Cryptanalysis• Cryptanalysts• Cryptology• Keys • Keyspace• Hashing
Symmetric Encryption(Single Key)
How big are keys?
• 128? Has 2128 possible values– The total lifetime of the universe is about 261
seconds.– Number of atoms in the earth 2170
– Number of atoms in the sun 2190
– Number of atoms in the universe 2265
Algorithms'
• Stream Ciphers (1 bit at a time)• Block Ciphers (Chunks at a time, AES uses 128
bit blocks)• Examples– DES, 3DES (No Longer Used)– Twofish, Serpent, AES, Blowfish, CAST5, RC4,
TDES, IDEA
Symmetric Encryption
• DES (Data Encryption Standard)– 56 Bit– Federal Information Processing Standard (FIPS 46) in 1976– 1997: RSA contest won by distributed crack (10,000 clients)– 1998: EFF built a $250K machine to crack DES in 2 days
• 2002 AES (May 26th, 2002)– 5 Finalists (Mars,RC6,Rijndael,Serpent,Twofish)– 128, 192, 256 bit keys.– The largest successful publicly-known brute force
attack has been against a 64-bit RC5 key by distributed.net (http://en.wikipedia.org/wiki/Advanced_Encryption_Standard)
Symmetric Encryption• 128-bit encryption
– 3 x 1038
– 1 modern computer needs 1024 years to crack 128-bit– 1 billion modern computers need 1015 years to crack– 1 billion modern computers need 1053 years to crack 256-bit– Some other cracking method required
• Other avenues are far easier:– Spyware/Rootkits– Social Engineering– Phishing– Password cracking
• Reference (The Struggle Between Unbreakable Encryption and Stupid Passwords By Brian Basgen [email protected])
Asymmetric Encryption2-key
Asymmetric Algorithms’
• Diffie-Hellman• DSS• ElGamal – Based off of Diffie-Hellman• RSA• Cramer-Shoup
XOR
• Secret Splitting• Secret Sharing
Hashing
• Digital Fingerprint– MD5– SHA-1
Algorithm Output size (bits)
Internal state size (bits)
Block size (bits)
Max message size (bits)
Word size (bits) Rounds Operations Collision
SHA-0 160 160 512 264 − 1 32 80 +,and,or,xor,rotfl Yes
SHA-1 160 160 512 264 − 1 32 80 +,and,or,xor,rotfl 263 attack
SHA-256/224 256/224 256 512 264 − 1 32 64 +,and,or,xor,
shr,rotfr None yet
SHA-512/384 512/384 512 1024 2128 − 1 64 80 +,and,or,xor,
shr,rotfr None yet
http://en.wikipedia.org/wiki/Sha1
Digital Signatures
• Signing uses Private Key• Verifying uses Public Key• “Authentication” of message.• Hash Message. Sign Hash. Send message with
Encrypted Hash.• Receiver decrypts hash with public key and
then matches hash sent with hash of message.
PKI
Digital Certificates
• Binds a name to a public key.• X.509 Standard• Registration with CA – Software, hardware, procedures, policies, people– RA Responsible for verification– Class 1 – Email– Class 2 – Software signing– Class 3 – Be own CA
Digital Certificates
• Key Pair Generation• Cert creation• Cert distribution• Key backup and recovery