Final answer:
In this cryptosystem, the encryption function adds the key modulo 101 to the plaintext, and the decryption function subtracts the key modulo 10 from the ciphertext. To decrypt the collected ciphertexts, apply the decryption function to each of them.
Step-by-step explanation:
In this cryptosystem, where P=C=k=Z101 and Ek(x)=x+kmod101, and Dk(y)=y−kmod10, the encryption function Ek(x) adds the key modulo 101 to the plaintext x, and the decryption function Dk(y) subtracts the key modulo 10 from the ciphertext y. Suppose you have collected n ciphertexts y1,y2…. To decrypt these ciphertexts, you need to apply the decryption function Dk(y) to each of them.
For example, if k=5 and y1=34, applying Dk(y1) would give (34-5)mod101 = 29mod101 = 29. So the decrypted plaintext corresponding to y1 is 29.
You can repeat this process for each of the ciphertexts you have collected to obtain the corresponding plaintexts.