## Substitution Cipher (by Michelle So)

What is the
problem with the encryption?

The problem
with this substitution encryption is in order for someone to use this code;
someone has to provide the key beforehand. In addition to this, using a
frequency analysis, one can easily decipher the message, as there are some
letters in the English language that occur more than other letters.

How do you
overcome this problem?

To overcome this problem, they could make the
code more complicated by adding an encryption to the key. If there was an
encryption to the key, it would take more time for the enemy to decipher it. Furthermore,
if the key was renew every day, by the time they have decode the encryption,
there would already be another key.

#exploremaths

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## Substitution Cipher (sophia kim)

CRYPTOGRAPHY.

What is the problem with substitution
ciphers?

Substitution cipher is fairly easy to
decipher using frequency analysis. Frequency analysis is the frequency of each
letter appearing in the cipher.

Ways to make it more difficult are:

Using different languages

Stacking several ciphers together

Using difficult symbols

Switching letters around

#exploremaths

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## Cryptography: Terrence Wong

The substitution method has a major flaw in it saying that it can be cracked with frequency analysis. Frequency analysis is the analysis of letters which appear frequently in a message or a text. One way to solve this issue is to replace letters with Greek Letters and manipulate it in a way of making it look miscellaneous. Letters could be replaced with different stroked which have been previously agreed on by the sender and receiver.

i.e.

You could have one stroke meaning ‘A’, a cross meaing ‘B’, two horizontal strokes and a vertical meaning ‘C’, and so on.

#exploremaths

## The Substitution Cipher [Adam Tan]

1. What is one problem with the substitution cipher?
One problem with this particular cipher is that it is reeeaaaasonably easy to break using ‘frequency analysis.’ By calculating how many times a certain letter occurs, referencing the frequency of understandable letters allows the decipherer(?) to assume which letters/numbers/symbols correspond to which letters.

2. How can this problem be overcome?

One way to overcome this obstacle is to substitute spaces with a combination of letters (a combination is necessary as a single letter may be confused with another letter. Another method is to place certain symbols after certain letters are written (eg. after every letter ‘A’, you can place an the letters ‘EN’. I received this idea from the beloved series Deltora Quest).

#exploremaths

## substitution cipher

1. The problem
The substitution cipher can be easily cracked from a simple method of frequency analysis. Frequency analysis is a measuring of counts a letter appears in a text. as E is the most frequently used letter in the alphabet, one can crack the code by finding the most frequently used letter in a code, and find out the key to read the code.

2. the solution

The solution I came up with is this.

– make a pattern of numbers. (e.g. 1-2-3-4-5)

– make a pattern of directions (e.g. left, right, left, right)

– Choose how to substitute letters (e.g. plus 1, therefore A=B, B=C)

– Apply these patterns to a code such as I like Pie.

Therefore the code for I like Pie will be

HNFOKOKB

#exploremaths

## Substitution Cipher (Hiya Ganju)

The main problem with the encryption method is that it can be
easily deciphered using frequency analysis. Frequency analysis is effective to
break down the encryption method because all the letters of the alphabet are in
order, meaning that when one letter code has been cracked, all the others are
also easy to crack, further leading to its inefficiency.

In order to prevent this from happening, the use of symbols,
different languages and various methods of encryption should be applied. This
will result in the reduction of deciphering the encryption method using the
frequency method or at least, make it more difficult.

#exploremaths

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## Substitution Cipher (by Sandeep Darapuneni)

#exploremaths

The substitution
cipher has one glaring problem to it; that frequency analysis of the symbols used
can be compared with the usage of the English letters to find out what a
message means. But this method is only effective when used on long messages. It
is kind of like reliability in science. If someone could send multiple short
messages, it would mean that it could be harder to break.

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## The Substitution Cipher (Eric Sun)

A major flaw in the alphabet shifting method is that it
could be easily solved using frequency analysis. A way that you could alter the
code: Substitute all the letters for something else like numbers or Greek
letters and mirror image the message.

#exploremaths

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## Substitution Cipher (Josh Luong)

1. What is one problem with the substitution cipher?

Shown in the video, it is noticeable that this encryption
method was flawed because of how it was solvable using the frequency analysis.
Frequency analysis is when you find a common letter used in the English
alphabet such as ‘e’ and by finding another letter that is just as common and
using that code scheme to work out the whole message.

2.What is one way to overcome this problem?

A way that we could solve this problem is by not only
encrypting the message 1 way but multiple. For example we could make the
message translated into several other languages that use the same shapes as the
letters in the English alphabet such as French or German then  that way the message will have another
process that it must be solved before readable.

#exploremaths

## Alphabet Shifting Cipher (Alex Ho)

The alphabet shifting cipher, although useful for mixing up
the letters, has its own flaw. Frequency analysis. The use of finding common
letters forming a small word can easily destroy the point of a cipher. Finding
just a couple of letters, and matching them up will lead to the match up of the
other missing letters without the person ever having to work them out.

To make this method better would be using more fancy words
and synonyms of common words, to allude the cracker. Another would be to use a
completely different cipher with different symbols and keys.

#exploremaths