Lab-3 Task 7 completed

Lab-3/Task-7/Readme.md

@@ -1 +1,71 @@
-# Task - 7 : 
+# Task - 7 : Keyed hash and HMAC
+
+The instructions are followed in the following steps:
+
+1. Create a text file and add some text. I named it [text.txt](text.txt). Now copy the text inside and paste into a new text file named [for-md5.txt](for-md5.txt).
+2. Generate the hash value H1 for this file using `MD5` hash algorithm using the following command:
+    ```
+    openssl dgst -md5 -hmac "this is task 7" for-md5.txt
+    ```
+    Generated Hash, H1:
+    ```
+    482c48d5234eff1ca0a1cb3f6d47f8fc
+    ```
+3. Open the file using `HEX Workshop` and change one bit (any bit) of the file. HEX workshop is used to edit binary files.
+4. Again generate the hash value H2 for this modified file.
+    ```
+    openssl dgst -md5 -hmac "this is task 7" for-md5.txt
+    ```
+    Generated Hash, H2:
+    ```
+    823a13f73f84674bd64ec678e074ef16
+    ```
+5. Hash value, H1 and H2 are not same. Following code is used to calculate how many bits are same between them.
+    ```py
+    def checkSame(h1, h2):
+        i = 0
+        cnt = 0
+        for ch in h1:
+            if ch==h2[i]:
+                cnt = cnt + 1
+            i = i + 1
+        
+        print("Number of same bit: ", cnt)
+
+    h1 = "482c48d5234eff1ca0a1cb3f6d47f8fc"
+    h2 = "823a13f73f84674bd64ec678e074ef16"
+
+    checkSame(h1, h2)
+    ```
+
+    Output:
+    ```
+    Number of same bit : 1
+    ```
+    Changing only one bit has changed the hash value. Only one bit is same as before in the hash value.
+
+<br>
+
+Now let's repeat the instructions for `SHA-256` algorithm.
+
+Copy the text of [text.txt](text.txt) and paste into a new file named [for-sha256.txt](for-sha256.txt)
+
+- Generate the hash value, H1 for this file using `SHA-256` algorithm using the following command:
+    ```
+    openssl dgst -sha256 -hmac "this is task 7" for-sha256.txt
+    ```
+    Generated Hash, H1:
+    ```
+    3f99d45079d1ad2dd1310ffc66f6bc92e6c119cde8cf093b5dadbcb62b1a1945
+    ```
+- After changing a bit in the file, Generated Hash, H2:
+    ```
+    45837b84493aefc8b6ae765ecc39112563f221de67a2d372efed28a5b6c87e50
+    ```
+- Run the [count.py](count.py) with the hash value H1 and H2.
+    ```
+    Number of same bit : 2
+    ```
+So, any single modification in the source file will change hash value to a great extent.
+
+This property of hash functions is widely used in various applications for data integrity verification, digital signatures, and detecting unauthorized modifications.

Lab-3/Task-7/count.py

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+def checkSame(h1, h2):
+    i = 0
+    cnt = 0
+    for ch in h1:
+        if ch==h2[i]:
+            cnt = cnt + 1
+        i = i + 1
+
+    print("Number of same bit: ", cnt)
+
+h1 = "482c48d5234eff1ca0a1cb3f6d47f8fc"
+h2 = "823a13f73f84674bd64ec678e074ef16"
+
+checkSame(h1, h2)

Lab-3/Task-7/for-md5.txt

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+In this one we are generating!one-way hash functions using MD5 and SHA256. We will generate hash value h1, flip one bit of the file, generate hash value h2 for modified file. Then check if h1 and h2 are similar or not, also need to write a program to count how many bits are same between them.

Lab-3/Task-7/for-sha256.txt

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+In this one we are generating!one-way hash functions using MD5 and SHA256. We will generate hash value h1, flip one bit of the file, generate hash value h2 for modified file. Then check if h1 and h2 are similar or not, also need to write a program to count how many bits are same between them.

Lab-3/Task-7/text.txt

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+In this one we are generating one-way hash functions using MD5 and SHA256. We will generate hash value h1, flip one bit of the file, generate hash value h2 for modified file. Then check if h1 and h2 are similar or not, also need to write a program to count how many bits are same between them.