Add script and write readme.

README.md

@@ -1,3 +1,21 @@
 # timelock
 
-Generate passwords in time.
+This program allows you to generate a password by hashing an input phrase a
+billion times. You can then use the output as a password.
+
+After using the password, you throw it away. If you need the password again, you can
+recover it via the original phrase and hash count.
+
+This tool is useful for other apps that lock you out from specific websites and
+can be password protected to do so.
+
+Here is how to use the script:
+
+```
+python timelock.py
+Enter count: 1e8
+Password: <password>
+Confirm password: <password>
+100000000 hashes done in 106.24s. Final result:
+fe90e6ccb7eb50ddf8237417b2ef8380396285a31d143a880572420206f041c9
+```

timelock.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+
+import hashlib
+import time
+import getpass
+
+
+def get_input():
+    total_count = 0
+    while not total_count:
+        try:
+            total_count = int(float(input("Enter count: ")))
+        except ValueError:
+            print("Enter a positive integer.")
+
+    seed, seed_check = "a", "b"
+    while seed != seed_check:
+        seed = getpass.getpass()
+        seed_check = getpass.getpass(prompt="Confirm password: ")
+        if seed != seed_check:
+            print("Passwords must match.")
+    return total_count, seed
+
+
+def print_progress(total_count, passed_time, current_count):
+    projected_time = total_count * passed_time / current_count
+    progress_time = "[{:.2f} / {:.2f}s".format(passed_time, projected_time)
+    progress_percent = current_count / total_count * 100
+    progress_percent = "- {:.2f}%]".format(progress_percent)
+    print(progress_time, progress_percent, "   ", end='\r')
+
+
+if __name__ == "__main__":
+    total_count, seed = get_input()
+
+    start_time = time.time()
+    current_time = start_time
+    m = hashlib.sha256()
+    m.update(seed.encode())
+
+    for current_count in range(total_count):
+        if time.time() - current_time > 1:
+            current_time = time.time()
+            passed_time = current_time - start_time
+            print_progress(total_count, passed_time, current_count)
+        m.update(m.digest())
+
+    time_passed = time.time() - start_time
+    print(f"{total_count} hashes done in {time_passed:.2f}s. Final result:")
+    print(m.hexdigest())