def key():
    message = entry_in.get()
    offset1 = sample(range(1, len(message) + 1), len(message))
    entry_key.delete(0, 'end')
    entry_key.insert(0, ''.join(map(str, offset1)))

 root = form.Tk()
root.geometry('200x200')
lbl1 = form.Label(text='Введите текст').pack()
entry_in = form.Entry(width=30)
entry_in.pack()
lbl_key = form.Label(text='Ключ шифрования').pack()
entry_key = form.Entry(width=30, text='')
entry_key.pack()
lbl2 = form.Label(text='Зашифрованый текст').pack()
entry_out = form.Entry(width=30)
entry_out.pack()
btn_key = form.Button(text='Создать ключ', command=key)
btn_key.pack()
btn = form.Button(text='Шифрование', command=process)
btn.pack()
btn2 = form.Button(text='Дефишрование', command=process2)
btn2.pack()
root.mainloop()

 plaintext = 'Привет'
key = 2
ciphertext = [''] * key
for column in range(key):
        pointer = column
        while pointer < len(plaintext):
            ciphertext[column] += plaintext[pointer]
            print(ciphertext)
            pointer += key
            
print(''.join(ciphertext))