JSFH

Run these program first. You will need them below:

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

Let's do a Diffie-Hellman key exchange! We have the following values:

QyY+SSJwRzYiLUkqc2FmZXByaW1lR0YlNiMtSSJeRyUqcHJvdGVjdGVkRzYkIiIjIiRHIiIiIj5JImdHRiUtSSlwcmltcm9vdEdGJTYkIjAoZSFSc2UlUj9GJEYv

I'm Alice. I have already picked my secret key a and I have sent you the following value:

QyQ+SSJBRzYiIkd6TSNlInArP1AhW0EwKSopPSxzNmtGIiIi

You decided your secret key would be:

QyQ+SSJiRzYiIigsLCwiIiIi

I have received your B value, and I have used it to get the key k. I have taken a message, encoded it with mess2num to get a number m, and then encrypted that using the encryption function ek(m) = m+k (mod p). The resulting encrypted message is:

QyQ+SSJjRzYiIkg1dSVHLXksT0s8XlVhLmRpInpaRSQiIiI=

Your task: Find the values of B, k, and the original message m. Then decode m using num2mess(m). If everything went right, you should get a sentence that makes sense.

JSFH

2) Now let's do ElGamal. I am still Alice, and I'm still using the same p and m:

QyY+SSJwRzYiLUkqc2FmZXByaW1lR0YlNiMtSSJeRyUqcHJvdGVjdGVkRzYkIiIjIiRHIiIiIj5JImdHRiUtSSlwcmltcm9vdEdGJTYkIjAoZSFSc2UlUj9GJEYv

I have picked a super secret value a, and I have sent you the value A:

QyQ+SSJBRzYiIkhqPzQoM05KZiwhKipmMjVLNiVmWiMpPiIiIg==

Now, you will send me a message. Start with some text, encode it into a number m using mess2num, then encrypt it using ElGamal, then send me the values of c1 and c2. If you do it correctly, I will be able to decrypt your message and get your original text using num2mess. (Note: the encoded message m must be smaller than p. With the p I picked, you can encode any message with 18 characters or less.)

JSFH