Another version of the columnar transposition cipher is the cipher using a key word. In this cipher, we encrypt as follows: Given a key word, we remove all the duplicate characters in the key word. For example, if the key word is ‘SECRET’, we remove the second ‘E’ and use ‘SECRT’ as the key word. To encrypt, we form a table as follows: In the first row, we write down the key word. In the following rows, we write the plaintext. Suppose we want to encrypt the text ‘ATTACKATDAWN’. We make a table as follows

Then we read off the columns in alphabetical order. We first read the column under ‘C’, followed by the columns under ‘E’, ‘R’, ‘S’ and ‘T’. We get the cipher text TTX TAN ADX AKW CAX. To decrypt, we reverse the process. Note that, since we know the length of the keyword, we can find the length of the columns by dividing the length of the message by the length of the keyword. Given the ciphertext ‘HNDWUEOESSRORUTXLARFASUXTINOOGFNEGASTORX’ and the key word ‘LANCE’, find the plaintext

 Decrypt each of the following cipher texts:
i) Text: "CBBGYAEBBFZCFEPXYAEBB", encrypted with affine cipher
with key (7,2).
ii) Text:"KSTYZKESLNZUV", encrypted with Vigenère cipher with key "RESULT"

Let f(x) = x ⁴ +x+1 ∈ F2[x]. We represent the field F_{2 4} by F2[x]/(f(x)). Let us write γ = x+ (f(x)). The table of values is given below:

i ) Prepare logarithm and antilogarithm tables as given in page 23 of block 1.

Let f(x) = x ³ −x−1 ∈ Z₅[x]. Find the product of x ² +2x+1+ (f(x)) and x ² +3x−1+ (f(x)) using the algorithm in page 23, block 1. You should show all the steps as in example 11, page 22, block 1.

Unit Plan

BICS and CALP

One-to-One Correspondence

Process Skills

Embedded Phonics

“A child’s scribbles should be considered as writing.” Discuss the statement.

Why should EVS be integrated with Language and Mathematics during the early primary years?

How can the skill of estimation be developed and nurtured with the help of various other mathematical concepts? Choose one concept (Number, Addition, Subtraction, and Measurement) and discuss

What do you understand by the term ‘Balance’ in the Balanced Comprehensive Approach to Literacy?

How would you use an everyday experience from the children’s life to teach them skill of data handling? Discuss with the help of an example.

List various concepts, process skills, values, and attitudes that can be developed while teaching the theme of ‘Water’ to Grade 2 children. Also briefly share three activities/strategies you would use to develop these.

Discuss with the help of an example what happens if diversity is not respected in the classroom and how it is a resource in the EVS learning of children.

How is the oral language treated in a typical/traditional classroom? What are its implication for the child’s language and literacy development?

Language and thinking are interlinked and support the development of each other. Discuss!

Often children show a lack of understanding of the concept of place value while doing addition problems. Why does it happen? Discuss the correct way of introducing children to the concept of place value and addition.

Often children are taught counting by making them recite and copy number names in their notebooks. Why is this pedagogy problematic? Discuss the correct way of introducing children to counting.