diff --git a/0079_Passcode_derivation/0079_Passcode_derivation.py b/0079_Passcode_derivation/0079_Passcode_derivation.py
new file mode 100644
index 0000000..7448101
--- /dev/null
+++ b/0079_Passcode_derivation/0079_Passcode_derivation.py
@@ -0,0 +1,79 @@
+# A common security method used for online banking is
+# to ask the user for three random characters from a passcode.
+# For example, if the passcode was 531278,
+# they may ask for the 2nd, 3rd, and 5th characters
+# the expected reply would be: 317.
+
+# The text file, keylog.txt, contains fifty successful login attempts.
+
+# Given that the three characters are always asked for in order,
+# analyse the file so as to determine the shortest possible secret passcode of unknown length.
+
+
+################################################
+# TOO MUCH MEMORY FOR LONG KEY. TODO: OPTIMIZE #
+################################################
+
+
+from itertools import combinations, product
+
+import numpy as np
+
+
+def read_keylog(filename):
+    return np.loadtxt(filename, dtype=str, delimiter='\n')
+
+
+def get_digits(n):
+    return [int(i) for i in str(n)]
+
+
+def main():
+    keys_inserted_str = read_keylog("p079_keylog.txt")
+    # keys_inserted_str = ["317"]
+    
+    length = 5
+    digits_str = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
+    digits_int = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+    while True:
+        print("Searching for possible full keys with length:", length)
+            
+        possible_indices_str_arr = list(combinations(digits_int[:length], 3))
+
+        possible_full_keys_set = set("".join(key_list) for key_list in product(digits_str, repeat=length))
+        found_at_least_one_before = False
+        for key_inserted in keys_inserted_str:
+            print("Checking inserted key", key_inserted, ". Length of found possible full keys:", len(possible_full_keys_set))
+            possible_full_keys_for_this_inserted_key = set()
+            found_at_least_one_before_for_this_inserted_key = False
+
+            for possible_full_key in possible_full_keys_set:
+                for possible_index in possible_indices_str_arr:
+
+                    if possible_full_key[possible_index[0]] + \
+                        possible_full_key[possible_index[1]] + \
+                            possible_full_key[possible_index[2]] == key_inserted:
+                        possible_full_keys_for_this_inserted_key.add(possible_full_key)
+                        found_at_least_one_before_for_this_inserted_key = True
+
+            if found_at_least_one_before and len(possible_full_keys_set) == 0:
+                break
+            if found_at_least_one_before:
+                # intersect sets possible_full_keys_set and possible_full_keys_for_this_inserted_key
+                possible_full_keys_set = possible_full_keys_set.intersection(
+                    possible_full_keys_for_this_inserted_key
+                )
+            else:
+                possible_full_keys_set = possible_full_keys_for_this_inserted_key
+                found_at_least_one_before = found_at_least_one_before_for_this_inserted_key
+
+        if found_at_least_one_before and len(possible_full_keys_set) == 0:
+            # full key with that length not possible, increase length
+            print("Full key with that length", length, "not possible, increase length to", length + 1)
+            length += 1
+        else:
+            # found something
+            print("\nFound something. List of all possible full keys:", sorted(list(possible_full_keys_set)))
+            break
+    
+main()
diff --git a/0079_Passcode_derivation/p079_keylog.txt b/0079_Passcode_derivation/p079_keylog.txt
new file mode 100644
index 0000000..41f1567
--- /dev/null
+++ b/0079_Passcode_derivation/p079_keylog.txt
@@ -0,0 +1,50 @@
+319
+680
+180
+690
+129
+620
+762
+689
+762
+318
+368
+710
+720
+710
+629
+168
+160
+689
+716
+731
+736
+729
+316
+729
+729
+710
+769
+290
+719
+680
+318
+389
+162
+289
+162
+718
+729
+319
+790
+680
+890
+362
+319
+760
+316
+729
+380
+319
+728
+716