CRYPTO 101ISSA Raleigh

OUTLINE1. Historical Crypto2. XOR3. Modern Crypto4. HTTPS: TLS5. Resources

HISTORICAL CRYPTO1. Caesar Cipher2. Vigenère Cipher3. Enigma Machine4. One Time Pad

E T A O I N S H R D L U

ROT13When Light awakens, he finds the Death Note back in

his possession in the hospital room and hides it.

Jura Yvtug njnxraf, ur svaqf gur Qrngu Abgr onpx va uvfcbffrffvba va gur ubfcvgny ebbz naq uvqrf vg.

VIGENÈRE CIPHER

diverttroopstoeastridge completevictorycomplete

ENIGMA MACHINE

ONE TIME PADkey as long as messagekey is truly randomkey is used only one timeonly two copies of the key exist

XOREXCLUSIVE OR

Message "Alice"

binary 01100001 01101100 01101001 01100011 01100101

random 11001111 10100111 11001111 00000110 01101010

xor 10101110 11001011 10100110 01100101 00001111

message key cipher

Message

Key

Cipher

Taken from an example on cryptosmith.com.

⊕ =

message key cipher

⊕ =

c1

c2

= ⊕ km1

= ⊕ km2

⊕ = ⊕c1 c2 m1 m2

cipher1 cipher2 message1 message2⊕ = ⊕

MODERN CIPHERSSymmetric

StreamThe key is a streamXOR the key with plaintext

BlockAsymmetric (Public/Private)

BLOCK CIPHERECB

ECB

CBC

ASYMMETRIC

ASYMMETRIC

ASYMMETRIC

HTTPS: TLS

CHAIN OF TRUST

MAN IN THE MIDDLE

RESOURCESgchq.github.io/CyberChefcryptopals.comciphersbyritter.comsecurity.stackexchange.com/questionswww.crypto101.iohashkiller.co.ukid0-rsa.pub