EC-Council Certified Encryption Specialist
(ECES)
What is cryptography?
Noun -
A) The process or skill of communicating in or deciphering secret writings or ciphers
B) Secret writing
Origin -
Cryptography (or cryptology); derived from word kryptos which means "hidden", and
grafo, which means "write", is the study of message secrecy
Definition-
Cryptography is the science of altering communication so that it cannot be understood
without having the key
Interloper
a person who becomes involved in a place or situation where they are not wanted or are
considered not to belong.
History of cryptography
A) Hidden or secret writing is very old: People have been practicing hidden writing for at
least 3,000 years.
B) Until the latter part of the 20th century, cryptography was almost exclusively used by
military and government
Mono-Alphabetic Substitution
A) Most primitive cryptographic algorithms
B) Substitute one character of cipher text for each character of plain text
C) Caesar Cipher, Atbash Cipher, Affine Cipher, Rot13 Cipher
Caesar Cipher
A) First used by Julius Caesar
B) Every letter is shifted a fixed number of spaces to the left or the right in the alphabet
C) The shifting is the "key" for this algorithm
D) The shift is often called the "alphabet" being used.
Example "I Like Computers" shift 1 to left becomes "H Khjd Bnlotsdqr"
*Most common single-letter word is "A" and most common three-letter word is
"the". Most common two-letter combinations are "EE" and "OO"*
E) 128-bit number from AES (Advanced Encryption Standard)
Atbash Cipher
A) Hebrew Code that reverses alphabet. Example "A" becomes "Z", "B" becomes "Y"...
"A cat sleeps" becomes "Z "xzg hovvkh"
B) Used by Hebrew scribes copying the book of Jeremiah
C) Simple cipher not used in modern times
,Affine Cipher
any single-substitution alphabet cipher (also called mono-alphabet substitution) in which
each letter in the alphabet is mapped to some numeric value, permuted with some
relatively simple mathematical function, and then converted back to a letter
Example*in Caesar cipher, each letter is converted to a number, shifted by a
certain amount, and converted back to a letter*
Basic formula for affine cipher is "ax + b (modM)
M= size of alphabet = 26
x= plain text letter's numeric equivalent
b= shift
a= some multiple, in Caesar cipher = 1
Caesar cipher (using affine cipher)
1x + shift (mod26)
Rot13 Cipher
similar to Caesar cipher, but all letters are rotated 13 spots
Example "A CAT" becomes "N PNG"
Scytale
A) Cylinder tool used by the Greeks and often specifically attributed to the Spartans
B) Used to encrypt messages
C) Turning the cylinder produced different cipher texts
D) First used in 7th century BC by Greek poet Archilochus
E) Writer of message wraps parchment around a rod
F) Recipient uses a rod of the same diameter as one used to create message
G) Requires both parties to have same size rod, and same leather "key"
Single Substitution Weaknesses
A) Easy to break
B) Easily susceptible to brute force attacks, even by low end computers
Multi-Alphabet Substitution
,A) Also called "Poly-Alphabet Substitution"
B) Use of more than 1 alphabet in a cipher. (to make ciphers like Caesar and Atbash
more secure)
Example: With +1 -1 +2 since you add 1 to the first letter, subtract 1 from the second
letter, add 2 to the third letter, resets on the fourth letter... "A CAT" becomes "B BCA"
C) Examples of "Poly-Alphabet Substitution" ciphers are: Cipher Disk, Vigenere, and
Enigma Machine
Cipher Disk
A) Uses a physical device to encrypt (like scytale)
B) Invented by Leon Alberti in 1466
C) Physical disk, each time you turned disk...you created a new cipher
D) Literal disk used to encrypt plain text
Vigenere Cipher
A) Most widely known Poly-alphabet cipher
B) Created in 1553 by Giovan Battista Bellaso...misattributed to Blaise de Vigenere
C) Encrypted using a table and set of mono-alphabet ciphers using keyword
D) Used in 1800 and 1900s
Example:
Breaking the Vigenere Cipher
A) First person to break Vigenere Cipher was Friedrich Kaiski in 1863
Playfair Cipher
A) Invented in 1854 by Charles Wheatstone...named after Lord Playfair who promoted
its use
B) uses five-by-five table containing a keyword or key phrase. To generate the key
table, one would first fill in the spaces with the keyword (dropping duplicates), then filled
rest of spaces with letters from alphabet in order
C) to encrypt a message, you would break message into groups of two letters.
("CheeseBurger" becomes "Ch ee se Bu rg er")
ADFGVX Cipher
A) The first chiper used by the German Army during World World I
B) Invented by Colnel Fritz Nebel in 1918
C) Transposition cipher which used: A modified Polybius square, A single columnar
transposition, and a 36 letter alphabet
D) Extension of an earlier cipher called ADFGX
, Homophonic Substitution
A) One of the earlier attempts to make substitution ciphers more robust by masking the
letter frequencies. Plain text letters map to more than 1 cipher text symbol
B) Having a single character of plain text map to more than 1 character of cipher text
makes it more difficult to analyze homophonic substitution ciphers.
C) The nomenclator combined a codebook that had a table of homophonic substitutions
D) Originally the codebook used names of poeple, thus the term "nomenclator.
Example Mr. Smith could be XX, and Mr. Jones could be XYZ
Null Ciphers
A) message is hidden in unrelated text. Example sending a message like "We are
having breakfast at noon at the cafe. Would that be ok?"
B) Sender and recipient have prearranged to use a pattern, taking letters from the
message. Example 3, 20, 22, 27, 32, 48 would produce the word "attack"
Rail Fence Ciphers
A) May be the most widely known transposition cipher.
B) You take down the message you want to encrypt and alter each letter on a different
row
Example* The message "Attackatdawn" or "Attack at dawn" is written as Atcadw
taktan*
C) Next you take it and write it out from left to right
Example Atcadwtaktan
D) To decrpyt, reverse the steps
E) Most texts use two rows, but it can be done with any number of rows
The Enigma Machine
A) In World War II, the Germans made use of an electromechanical rotor based cipher
system known as The Enigma Machine
B) Designed so that when the operator pressed a key the encrypted cipher text for that
plain text was different each time
Example When the operator pressed the "A" key, it might generate an "F" this
time, and might generate a "D" next time
C) Multi-alphabet cipher consisting of 26 possible alphabets
D) Allied cipher machines in WWII included the British TypeX and the American
SIGABA (both were similar to Enigma machine, but contained improvements and more
security)
CrypTool
A) allows you to enter in any text, choose the historic algorithm you want to use, then
encrypt that text in a matter of seconds
http://www.cryptool.org
B) You can easily use CrypTool to perform RSA encryption You simply need to
provide the plaintext and two large prime numbers to create the public and
private keys
(ECES)
What is cryptography?
Noun -
A) The process or skill of communicating in or deciphering secret writings or ciphers
B) Secret writing
Origin -
Cryptography (or cryptology); derived from word kryptos which means "hidden", and
grafo, which means "write", is the study of message secrecy
Definition-
Cryptography is the science of altering communication so that it cannot be understood
without having the key
Interloper
a person who becomes involved in a place or situation where they are not wanted or are
considered not to belong.
History of cryptography
A) Hidden or secret writing is very old: People have been practicing hidden writing for at
least 3,000 years.
B) Until the latter part of the 20th century, cryptography was almost exclusively used by
military and government
Mono-Alphabetic Substitution
A) Most primitive cryptographic algorithms
B) Substitute one character of cipher text for each character of plain text
C) Caesar Cipher, Atbash Cipher, Affine Cipher, Rot13 Cipher
Caesar Cipher
A) First used by Julius Caesar
B) Every letter is shifted a fixed number of spaces to the left or the right in the alphabet
C) The shifting is the "key" for this algorithm
D) The shift is often called the "alphabet" being used.
Example "I Like Computers" shift 1 to left becomes "H Khjd Bnlotsdqr"
*Most common single-letter word is "A" and most common three-letter word is
"the". Most common two-letter combinations are "EE" and "OO"*
E) 128-bit number from AES (Advanced Encryption Standard)
Atbash Cipher
A) Hebrew Code that reverses alphabet. Example "A" becomes "Z", "B" becomes "Y"...
"A cat sleeps" becomes "Z "xzg hovvkh"
B) Used by Hebrew scribes copying the book of Jeremiah
C) Simple cipher not used in modern times
,Affine Cipher
any single-substitution alphabet cipher (also called mono-alphabet substitution) in which
each letter in the alphabet is mapped to some numeric value, permuted with some
relatively simple mathematical function, and then converted back to a letter
Example*in Caesar cipher, each letter is converted to a number, shifted by a
certain amount, and converted back to a letter*
Basic formula for affine cipher is "ax + b (modM)
M= size of alphabet = 26
x= plain text letter's numeric equivalent
b= shift
a= some multiple, in Caesar cipher = 1
Caesar cipher (using affine cipher)
1x + shift (mod26)
Rot13 Cipher
similar to Caesar cipher, but all letters are rotated 13 spots
Example "A CAT" becomes "N PNG"
Scytale
A) Cylinder tool used by the Greeks and often specifically attributed to the Spartans
B) Used to encrypt messages
C) Turning the cylinder produced different cipher texts
D) First used in 7th century BC by Greek poet Archilochus
E) Writer of message wraps parchment around a rod
F) Recipient uses a rod of the same diameter as one used to create message
G) Requires both parties to have same size rod, and same leather "key"
Single Substitution Weaknesses
A) Easy to break
B) Easily susceptible to brute force attacks, even by low end computers
Multi-Alphabet Substitution
,A) Also called "Poly-Alphabet Substitution"
B) Use of more than 1 alphabet in a cipher. (to make ciphers like Caesar and Atbash
more secure)
Example: With +1 -1 +2 since you add 1 to the first letter, subtract 1 from the second
letter, add 2 to the third letter, resets on the fourth letter... "A CAT" becomes "B BCA"
C) Examples of "Poly-Alphabet Substitution" ciphers are: Cipher Disk, Vigenere, and
Enigma Machine
Cipher Disk
A) Uses a physical device to encrypt (like scytale)
B) Invented by Leon Alberti in 1466
C) Physical disk, each time you turned disk...you created a new cipher
D) Literal disk used to encrypt plain text
Vigenere Cipher
A) Most widely known Poly-alphabet cipher
B) Created in 1553 by Giovan Battista Bellaso...misattributed to Blaise de Vigenere
C) Encrypted using a table and set of mono-alphabet ciphers using keyword
D) Used in 1800 and 1900s
Example:
Breaking the Vigenere Cipher
A) First person to break Vigenere Cipher was Friedrich Kaiski in 1863
Playfair Cipher
A) Invented in 1854 by Charles Wheatstone...named after Lord Playfair who promoted
its use
B) uses five-by-five table containing a keyword or key phrase. To generate the key
table, one would first fill in the spaces with the keyword (dropping duplicates), then filled
rest of spaces with letters from alphabet in order
C) to encrypt a message, you would break message into groups of two letters.
("CheeseBurger" becomes "Ch ee se Bu rg er")
ADFGVX Cipher
A) The first chiper used by the German Army during World World I
B) Invented by Colnel Fritz Nebel in 1918
C) Transposition cipher which used: A modified Polybius square, A single columnar
transposition, and a 36 letter alphabet
D) Extension of an earlier cipher called ADFGX
, Homophonic Substitution
A) One of the earlier attempts to make substitution ciphers more robust by masking the
letter frequencies. Plain text letters map to more than 1 cipher text symbol
B) Having a single character of plain text map to more than 1 character of cipher text
makes it more difficult to analyze homophonic substitution ciphers.
C) The nomenclator combined a codebook that had a table of homophonic substitutions
D) Originally the codebook used names of poeple, thus the term "nomenclator.
Example Mr. Smith could be XX, and Mr. Jones could be XYZ
Null Ciphers
A) message is hidden in unrelated text. Example sending a message like "We are
having breakfast at noon at the cafe. Would that be ok?"
B) Sender and recipient have prearranged to use a pattern, taking letters from the
message. Example 3, 20, 22, 27, 32, 48 would produce the word "attack"
Rail Fence Ciphers
A) May be the most widely known transposition cipher.
B) You take down the message you want to encrypt and alter each letter on a different
row
Example* The message "Attackatdawn" or "Attack at dawn" is written as Atcadw
taktan*
C) Next you take it and write it out from left to right
Example Atcadwtaktan
D) To decrpyt, reverse the steps
E) Most texts use two rows, but it can be done with any number of rows
The Enigma Machine
A) In World War II, the Germans made use of an electromechanical rotor based cipher
system known as The Enigma Machine
B) Designed so that when the operator pressed a key the encrypted cipher text for that
plain text was different each time
Example When the operator pressed the "A" key, it might generate an "F" this
time, and might generate a "D" next time
C) Multi-alphabet cipher consisting of 26 possible alphabets
D) Allied cipher machines in WWII included the British TypeX and the American
SIGABA (both were similar to Enigma machine, but contained improvements and more
security)
CrypTool
A) allows you to enter in any text, choose the historic algorithm you want to use, then
encrypt that text in a matter of seconds
http://www.cryptool.org
B) You can easily use CrypTool to perform RSA encryption You simply need to
provide the plaintext and two large prime numbers to create the public and
private keys
