diff --git a/src/cipher_analytical_machine/ciphers/simple_substitution.clj b/src/cipher_analytical_machine/ciphers/simple_substitution.clj
index 365f405..95e1d6b 100644
--- a/src/cipher_analytical_machine/ciphers/simple_substitution.clj
+++ b/src/cipher_analytical_machine/ciphers/simple_substitution.clj
@@ -44,15 +44,26 @@
       (caesar/encrypt-message key symbols)
       (encrypt-message substitution-table)))
 
+(defn decrypt-by-table
+  "Decrypt a message by the substitution-table"
+  [substitution-table message]
+  (map (fn [char] (find-value-in-table char substitution-table)) message))
+
+(defn decrypt-message-by-symbol-table
+  "Decrypt a message using the simple substitution cipher. The function is case-insensitive. The substitution-table must be (symbols, symbols)."
+  [substitution-table message ]
+  (->> message
+       (decrypt-by-table substitution-table)
+       (remove nil?)
+       (cs/join)))
+
 (defn decrypt-message
-  "Decrypt a message using the simple substitution cipher. The function is case-insensitive. The substitution-table must be "
+  "Decrypt a message using the simple substitution cipher. The function is case-insensitive. The substitution-table must be (int, symbols)."
   [message substitution-table]
   (let [message (cs/split message #",")]
     (->> message
          (map #(Integer/parseInt %))
-         (map (fn [char] (find-value-in-table char substitution-table)))
-         (remove nil?)
-         (cs/join))))
+         (decrypt-message-by-symbol-table substitution-table))))
 
 (defn decrypt-message-with-caesar
   "Decrypt a message using the simple substitution cipher and the Caesar cipher. The function is case-insensitive."
diff --git a/test/cipher_analytical_machine/ciphers/simple_substitution_test.clj b/test/cipher_analytical_machine/ciphers/simple_substitution_test.clj
index 6e6495c..5eac042 100644
--- a/test/cipher_analytical_machine/ciphers/simple_substitution_test.clj
+++ b/test/cipher_analytical_machine/ciphers/simple_substitution_test.clj
@@ -48,6 +48,23 @@
         "abc" 1 "2,3,1"
         "aDbdc" 0 "1,2,3"))))
 
+(deftest decrypt-by-table-test
+  (let [table {\d \a \e \b \f \c}]
+    (testing "The function must decrypt the message by the table."
+      (are [message expected]
+          (= expected (decrypt-by-table table message))
+        "def" '(\a \b \c)
+        "abf" '(nil nil \c)
+        "fed" '(\c \b \a)))))
+
+(deftest decrypt-message-by-symbol-table-test
+  (let [table {\d \a \e \b \f \c}]
+    (testing "The function must decrypt the message and remove unknown numbers."
+      (are [message expected]
+          (= expected (decrypt-message-by-symbol-table table message))
+        "def" "abc"
+        "daef" "abc"))))
+
 (deftest decrypt-message-test
   (let [table {1 \a 2 \b 3 \c}]
     (testing "The function must decrypt the message and remove unknown numbers."