CPH Unit 8

Cryptoanalysis

The field of code breaking.

Bruteforce

The method of trying all possibilities, leveraging a computer's speed to perform millions of calculations quickly.

Rail-fence Cipher

A cipher method that is easily broken; its security relies on the number of rails used.

Minmax Pattern

A technique where the decrypted word list with the most known words is remembered by updating maxGoodsoFar.

Row-Major Order

An order of cell storage that saves all values of the first row first, followed by the second row, and so forth.

Column-Major Order

An order of cell storage that saves all values of the first column first, followed by the second column, and so forth.

Substitution Cipher

A more complex cipher that is difficult to crack with brute force, allowing for pattern analysis of frequently used letters.

In-place sort

A sorting method that modifies the existing list without creating a new list or returning a new value.

Frequency Analysis

A method for breaking encryption that analyzes letter frequency in a text.

Pattern Matchings

Finding a word from the dictionary that matches the length and letters of a partially decoded ciphertext.

Regular Expressions

Tools for matching strings that allow the use of wildcard characters, enhancing flexibility in matching.

Capture Group

Characters grouped in a regular expression that help identify which parts of the target word match pattern letters.

.join(list)

String method that returns a string composed of the elements in the list, separated by the string used to call the method

sort(key = none, reverse = false)

Performs an in-place sort of the list— that is, the list is modified Keyword Parameters: key: specifies a function to used for comparing items; default is none, which means to sort on the first element reverse: specifies whether the list should be sorted in reverse (high to low); default is low to high (False)

setDefault(key, default)

If the key is not in the dictionary, insert key with a value of default and return default. If the key is in the dictionary, return the value for the key

zip(list1, list2, …)

Iterator that returns tuples composed of parallel elements of each list

match(pattern, string)

Matches any string in myString that starts with a, b, or c followed by XY followed by any character. Returns a Match on success or None

sub(pattern, replacement, string)

Returns ‘XxyzbgXX’. Like replace, except uses regular expression matching.

findall(pattern, string)

Returns [‘bc’, ‘cb’]. Returns a list of all substrings matching the regular expression

groups()

Returns a tuple of all capture groups matched. matchObj is created by a call to match.

groups(i)

Returns a single capture group at index i. matchObj is created by a call to match.