diff --git a/ex06/input.txt b/ex06/input.txt
new file mode 100644
index 0000000..cecdb81
--- /dev/null
+++ b/ex06/input.txt
@@ -0,0 +1,64 @@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diff --git a/ex06/main.c b/ex06/main.c
new file mode 100644
index 0000000..167c594
--- /dev/null
+++ b/ex06/main.c
@@ -0,0 +1,28 @@
+#include "utils.h"
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <filename>\n", argv[0]);
+    return EXIT_FAILURE;
+  }
+
+  const char *filename = argv[1];
+
+  FILE *fp = fopen(filename, "r");
+  if (fp == NULL) {
+    printf("Error opening file %s\n", filename);
+    return EXIT_FAILURE;
+  }
+
+  printf("%u\n", hamming("this is a test", "wokka wokka!!!"));
+
+  if (fclose(fp)) {
+    printf("Error closing file %s\n", filename);
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}
diff --git a/meson.build b/meson.build
index cb25814..0d0f588 100644
--- a/meson.build
+++ b/meson.build
@@ -8,3 +8,4 @@ executable('ex02', ['ex02/main.c', 'utils.c'], dependencies: m_dep)
 executable('ex03', ['ex03/main.c', 'utils.c'], dependencies: m_dep)
 executable('ex04', ['ex04/main.c', 'utils.c'], dependencies: m_dep)
 executable('ex05', ['ex05/main.c', 'utils.c'], dependencies: m_dep)
+executable('ex06', ['ex06/main.c', 'utils.c'], dependencies: m_dep)
diff --git a/utils.c b/utils.c
index f77e849..c79eb32 100644
--- a/utils.c
+++ b/utils.c
@@ -3,6 +3,20 @@
 #include <math.h>
 #include <string.h>
 
+#define min(a, b)                                                              \
+  ({                                                                           \
+    __typeof__(a) _a = (a);                                                    \
+    __typeof__(b) _b = (b);                                                    \
+    _a > _b ? _b : _a;                                                         \
+  })
+
+#define max(a, b)                                                              \
+  ({                                                                           \
+    __typeof__(a) _a = (a);                                                    \
+    __typeof__(b) _b = (b);                                                    \
+    _a > _b ? _a : _b;                                                         \
+  })
+
 unsigned char hex_to_byte(const char c) {
   if (isdigit(c)) {
     return c - '0';
@@ -69,3 +83,18 @@ double frequency_score(unsigned char *buf, size_t len) {
   }
   return chi2;
 }
+
+unsigned int hamming(const char *s1, const char *s2) {
+  unsigned int len1 = strlen(s1);
+  unsigned int len2 = strlen(s2);
+
+  unsigned int res = 0;
+  for (size_t i = 0; i < min(len1, len2); ++i) {
+    unsigned int n = s1[i] ^ s2[i];
+    while (n) {
+      res += n & 1;
+      n >>= 1;
+    }
+  }
+  return res;
+}
diff --git a/utils.h b/utils.h
index 3a5d463..dd090fb 100644
--- a/utils.h
+++ b/utils.h
@@ -8,5 +8,6 @@ size_t hex_to_bytes(unsigned char *out, const char hex[static 1]);
 unsigned char *bytes_to_base64(unsigned char *out,
                                const unsigned char in[static 1], size_t len);
 double frequency_score(unsigned char *buf, size_t len);
+unsigned int hamming(const char *s1, const char *s2);
 
 #endif /* UTILS_H */