AES algorithm - PowerPoint PPT Presentation

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AES algorithm

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  1. AES algorithm 128 bits/16 bytes Byte substitution Shift Row A round: Mix Column Key Addition

  2. 4 bytes AES algorithm a set of 16 bytes from the file to be encrypted B Y S T U E B s S H I R F O T W Mix column Mix column Mix column Mix column Ki,15 + K A E D Y D Ki,0 +

  3. SECURITY Cryptology cryptanalysis cryptography symmetric asymmetric protocols We are here stream block ciphers ciphers LFSR DES, 3DES, AES

  4. Asymmetric encryption https://youtube.com/watch?v=YEBfamv-_do&t=127s

  5. Asymmetric algorithms Diffe-Hellman first RSA most common Digitial Signature Algorithm U.S. Govt standard ECDSA elliptic curve XTR clever/esoteric field theory stuff Encrypt a file using a public key: opensslrsautl -encrypt -inkeypublic.pem -pubin -in file.txt -out file.ssl

  6. Generate a public/private key pair: $ opensslgenrsa -out private.pem 1024 Extract the public key: $ opensslrsa -in private.pem -out public.pem -outform PEM -pubout Encrypt a file using a public key: opensslrsautl -encrypt -inkeypublic.pem -pubin -in file.txt -out file.ssl Unencrypt using the private key: opensslrsautl -decrypt -inkeyprivate.pem -in file.ssl -out decrypted.txt

  7. $ cat private.pem -----BEGIN RSA PRIVATE KEY----- MIICXQIBAAKBgQChSCwe6Cut/MbQPrlFXCVJ/vCypeiDnHa//yerdeZ/zNR4oYZ1 d60dRc2Ro1nQNgJEissd9HTy/u4COlaShYHRzyiolCS39mi+hmRp2lRWMfdzBEdc nezeVlptSriGm0dl3bJG9J9EK3/QL25FH4lxHIXxGJY5ldCZOFldp/ITKwIDAQAB AoGAUEwzk0u6e4xvm7yu12aSNi4Uvo01n1kmEl9B6+7uTNC5NDoPTKrB6OIZABqZ G73YETIdAJP2KglcjIVpFtgbkoSUat08ZSKzs1lU/WJRJ7WAVBWPVeYyRdB6OIWs yguE8QuO4PGCG21no1SzgxHTp7Uv1r2RrvZDcHvcLNhK3+kCQQDTz6GNydhaav+L wzSC15AsyaMvy0rwh7NicJR27voDY8VA8WbpqYrt8Gby4yE/kpvRmF7ngjdiZwpU jgwDJVu3AkEAwu3jysmrLt2R76abxhvSr57TYpGGDraBQiK4lvzm61xMhnDMFIH9 sN5/pjQx6ojczWYpSliZn/Sgajn8aU6sLQJBAIw68c2Krdem8UsZ0OEzUDumv4h8 AkBex0/MEy7ups2pt0V4zVazrcw8FhyGbVPGf6zzQRnq5zoZ2AgFB0Tp7d8CQDlG HIAg8SM8Bv0bPvnegvEHAaUcjP8VsLT17rauaEsPO4zk55G/AANP3MHA5Em9HONc +RTXI4xUHC4aC4gFjaECQQCoTw66TwRaSKIS2x3vL8NYYmwo0wh7tbiJm1BhtUrH nGQ/KA4rEJZiUQVv2U50uyjR1mYQZ1ujeqeGmpvDdajS -----END RSA PRIVATE KEY-----

  8. $ cat public.pem -----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQChSCwe6Cut/MbQPrlFXCVJ/vCy peiDnHa//yerdeZ/zNR4oYZ1d60dRc2Ro1nQNgJEissd9HTy/u4COlaShYHRzyio lCS39mi+hmRp2lRWMfdzBEdcnezeVlptSriGm0dl3bJG9J9EK3/QL25FH4lxHIXx GJY5ldCZOFldp/ITKwIDAQAB -----END PUBLIC KEY-----

  9. Asymmetric encryption Symmetric encryption is much faster than public/private key encryption Leading to a hybrid system encrypt with symmetric, use public/private to transmit the key

  10. Asymmetric encryption

  11. Asymmetric encryption

  12. Keys are mathematically related as we’ve seen • encrypt with one key, decrypt with the other • given one key, the probability that you could derive the other is so close to zero that even Adi-Ananta-Seshi & Khowarizimi can’t tell the difference

  13. Consider the following scenarios with respect to the sender, the receiver, and eve: I encrypt something with your public key and send it to you I encrypt something with my public key and send it to you

  14. I encrypt something with my private key and send it to you I encrypt something with my private key I encrypt a second time with your pubic key then send it to you I encrypt something with your public key the encrypt a second time with your friend’s public key then send it to you

  15. “I encrypt with my private key” Mathematically sensible, but usually We say sign with the private key and verify with the public key + hash function + padding + usually separate key pair for signing

  16. Electronic signature • more general • distinct legal concept • standardization varies, as does acceptance and case law • NH 1869 – • enforceability of telegraphs as electronic signatures

  17. Digital signature – can be used to implement electronic signatures n • Existential forgery • Selective forgery • Universal forgery • Total break

  18. Existential forgery – adversaries can forge the signature of one message, but not the one they wanted Selective forgery – adversaries can forge the signature of a message of their choice Universal forgery – adversaries can forge the signature of any message though they don’t know the secret key Total break - adversaries know the secret key

  19. + hash function + padding + usually separate key pair for signing “I encrypt with my private key” Vulnerable to existential forgery Pick a random signature, use verification to determine the corresponding message Instead, we hash the message to produce a digest pad it out to a given length, then sign

  20. Digital signature Hash functions

  21. Hash tables Hash functions Enough data structures to see the connection Checksum Message digest Digital fingerprint Hash value

  22. Cryptographic hash function CHF MD5(lynx.cfg)= 1b734f5470ad18e362efcb11bd5907cc

  23. They share attributes • Deterministic – same hash every time given the same msg • 1 – way • Avalanche – small change in input = big change in output • Finding collisions is difficult • Finding the original msg is difficult • there are infinitely many, but this • is still worth considering

  24. DGST(1) OpenSSL DGST(1) NAME openssl-dgst, dgst, sha, sha1, mdc2, ripemd160, sha224, sha256, sha384,sha512, md2, md4, md5, dss1 - message digests SYNOPSIS openssldgst [-sha|-sha1|-mdc2|-ripemd160|-sha224|-sha256|-sha384| -sha512|-md2|-md4|-md5|-dss1] [-c] [-d] [-hex] [-binary] [-r] [-non-fips-allow] [-out filename] [-sign filename] [-keyformarg] [-passinarg] [-verify filename] [-prverify filename] [-signature filename] [-hmac key] [-non-fips-allow] [-fips-fingerprint] [file...]

  25. $ echo "hi" | openssldgst -sha256 (stdin)= 98ea6e4f216f2fb4b69fff9b3a44842c38686ca685f3f55dc48c5d3fb1107be4 rjoyce9@ITEC-480-E15748 /etc $ echo "hi " | openssldgst -sha256 (stdin)= 5400fc717d9b2543f5e24da4b2c52f196845455073fd7fcef704c792322a552c $ echo "hi" | openssldgst -sha256 (stdin)= 98ea6e4f216f2fb4b69fff9b3a44842c38686ca685f3f55dc48c5d3fb1107be4

  26. But necessarily suffer from collisions Add ASCII values of letters to hash the words in English == 95% collision rate 3 * hash table size

  27. And… you can’t go backwards You cannot decrypt a message digest to get the original document Why not?

  28. Crypt(3) DES Vs CHF’s

  29. rjoyce9@ITEC-480-E15748 /etc $ echo "this is much muchmuchmuchmuch longer than the length of the resulting digest and, given the same radix, implies collisions" | openssldgst -sha256 (stdin)= 11c5337d902b97bd8f0086a7394e52f0b9c2f2d1ddcaa2ccd6b8682ba42e5442

  30. In theory digital signatures will provide Authenticity Integrity Non-repudiation What are some weak spots here?

  31. I use your public key to encrypt a top secret document, then I send it to you. You use the corresponding private key to decrypt and read it What could possibly go wrong?

  32. Digital Certificates Proves the ownership of a public key (after all, how can you really be sure?) Information in the public key verify the private key and the validity of the certificate – can be independently verified

  33. Typically issued to a person or organization, but also to a computer or other device SSL - secure socket layer TLS - transport layer security (HTTPS)

  34. x.590 cert example here

  35. PKI – public key infrastructure scheme The overall roles, policies, procedures needed To make it all work over a large range of e-activities Certificates are issued by a CA – Certificate Authority https://m.youtube.com/watch?v=i-rtxrEz_E8

  36. Registration Authorities • The “GUI” for the CA • interface • payment • verification of identity documents • Certificate revocation lists • something changed • did you pay me yet?

  37. Root CA, imtermediate CA, hierarchy, chain of trust https://m.youtube.com/watch?v=heacxYUnFHA

  38. Web of Trust

  39. openssl – “robust, commercial-grade, and full-featured Toolkit for the Transport Layer Security (TLS) and Secure Socket Layer (SSL) protocols. It is also a general-purpose cryptography library. --openssl.org “Please put OpenSSL Out of Its Misery. OpenSSL must die, for it will never get any better”

  40. “OpenSSL is a terrible piece of software”. “/* The aim of right-shifting md_size is so that the compiler doesn’t figure out that it can remove div_spoiler as that would require it to prove that md_size is always even, which I hope is beyond it */ div_spoiler = md_size >> 1; “ **”proven” correct”**

  41. Cryptographic building blocks • Crypto-protocol designers • API design • Implementation programmers • Compiler design and code • Instruction set • Hardware • Million(s) of lines of code • get everything correct, then a maybe-not-exceptional • application developer can use it all without fault

  42. “CA Trustworthiness is a joke” – internet opinion (but not alone) TURKTRUST BILGI ILETISIM VE BILISM GUVENLIGI HIZMETLERI A.@. 8/2012 – issued bogus certificates A “one-time” mistake, “it can never happen again” ok…. Still, bottom line is that more complexity = more risk and we have complexity in spades

  43. Openssl – the big one NSS – Mozilla tools libreSSL – heartbleed response boringSSL – google’s version Pgp, openPGP – Pretty Good Privacy, encryption for the masses, Phil Zimmerman 1991 GPG – GNU Privacy Guard, implementation of the OpenPGP standard Kerberos – computer network authentication protocol allows proof-of-identity for devices talking over an insecure network on US Munitions List at the time due to DES Crypt/libcrypt

  44. MIDTERM in class Thursday 10 October 2019

  45. Cryptography Landscape Can you explain/combine/label/group these? DES Feistel network ZKP OTP Substitution D-H Digital signature Diffusion TRNG Symmetric encryption Elliptic Curve SHA PGP GPG X.509 AES Confusion LFSR Block cipher Galois Fields stream cipher Public Key Cryptography PKI RSA Digital Signature 3DES Trust Transposition CA MD5