diff --git a/src/libstd/md4.rs b/src/libstd/md4.rs
new file mode 100644
index 000000000000..b6ef12842a11
--- /dev/null
+++ b/src/libstd/md4.rs
@@ -0,0 +1,110 @@
+fn md4(msg: [u8]) -> {a: u32, b: u32, c: u32, d: u32} {
+    let orig_len = vec::len(msg) * 8u;
+    // pad message
+    let msg = msg + [0x80u8];
+    let bitlen = orig_len + 8u;
+    while (bitlen + 64u) % 512u > 0u {
+        msg += [0u8];
+        bitlen += 8u;
+    }
+    // append length
+    let i = 0u;
+    while i < 8u {
+        msg += [(orig_len >> (i * 8u)) as u8];
+        i += 1u;
+    }
+
+    let a = 0x67452301u32;
+    let b = 0xefcdab89u32;
+    let c = 0x98badcfeu32;
+    let d = 0x10325476u32;
+
+    fn rot(r: int, x: u32) -> u32 {
+        let r = r as u32;
+        (x << r) | (x >> (32u32 - r))
+    }
+
+    let i = 0u, e = vec::len(msg);
+    let x = vec::init_elt_mut(0u32, 16u);
+    while i < e {
+        let aa = a, bb = b, cc = c, dd = d;
+
+        let j = 0u, base = i;
+        while j < 16u {
+            x[j] = (msg[base] as u32) + (msg[base + 1u] as u32 << 8u32) +
+                (msg[base + 2u] as u32 << 16u32) +
+                (msg[base + 3u] as u32 << 24u32);
+            j += 1u; base += 4u;
+        }
+
+        let j = 0u;
+        while j < 16u {
+            a = rot(3, a + ((b & c) | (!b & d)) + x[j]);
+            j += 1u;
+            d = rot(7, d + ((a & b) | (!a & c)) + x[j]);
+            j += 1u;
+            c = rot(11, c + ((d & a) | (!d & b)) + x[j]);
+            j += 1u;
+            b = rot(19, b + ((c & d) | (!c & a)) + x[j]);
+            j += 1u;
+        }
+
+        let j = 0u, q = 0x5a827999u32;
+        while j < 4u {
+            a = rot(3, a + ((b & c) | ((b & d) | (c & d))) + x[j] + q);
+            d = rot(5, d + ((a & b) | ((a & c) | (b & c))) + x[j + 4u] + q);
+            c = rot(9, c + ((d & a) | ((d & b) | (a & b))) + x[j + 8u] + q);
+            b = rot(13, b + ((c & d) | ((c & a) | (d & a))) + x[j + 12u] + q);
+            j += 1u;
+        }
+
+        let j = 0u, q = 0x6ed9eba1u32;
+        while j < 8u {
+            let jj = j > 2u ? j - 3u : j;
+            a = rot(3, a + (b ^ c ^ d) + x[jj] + q);
+            d = rot(9, d + (a ^ b ^ c) + x[jj + 8u] + q);
+            c = rot(11, c + (d ^ a ^ b) + x[jj + 4u] + q);
+            b = rot(15, b + (c ^ d ^ a) + x[jj + 12u] + q);
+            j += 2u;
+        }
+
+        a += aa; b += bb; c += cc; d += dd;
+        i += 64u;
+    }
+    ret {a: a, b: b, c: c, d: d};
+}
+
+fn md4_str(msg: [u8]) -> str {
+    let {a, b, c, d} = md4(msg);
+    fn app(a: u32, b: u32, c: u32, d: u32, f: block(u32)) {
+        f(a); f(b); f(c); f(d);
+    }
+    let result = "";
+    app(a, b, c, d) {|u|
+        let i = 0u32;
+        while i < 4u32 {
+            let byte = (u >> (i * 8u32)) as u8;
+            if byte <= 16u8 { result += "0"; }
+            result += uint::to_str(byte as uint, 16u);
+            i += 1u32;
+        }
+    }
+    result
+}
+
+fn md4_text(msg: str) -> str { md4_str(str::bytes(msg)) }
+
+#[test]
+fn test_md4() {
+    assert md4_text("") == "31d6cfe0d16ae931b73c59d7e0c089c0";
+    assert md4_text("a") == "bde52cb31de33e46245e05fbdbd6fb24";
+    assert md4_text("abc") == "a448017aaf21d8525fc10ae87aa6729d";
+    assert md4_text("message digest") == "d9130a8164549fe818874806e1c7014b";
+    assert md4_text("abcdefghijklmnopqrstuvwxyz") ==
+        "d79e1c308aa5bbcdeea8ed63df412da9";
+    assert md4_text("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123\
+                     456789") == "043f8582f241db351ce627e153e7f0e4";
+    assert md4_text("12345678901234567890123456789012345678901234567890123456\
+                     789012345678901234567890") ==
+        "e33b4ddc9c38f2199c3e7b164fcc0536";
+}
diff --git a/src/libstd/std.rc b/src/libstd/std.rc
index c76497cfb7ea..d96b6b7b6666 100644
--- a/src/libstd/std.rc
+++ b/src/libstd/std.rc
@@ -57,6 +57,7 @@ mod getopts;
 mod json;
 mod rand;
 mod sha1;
+mod md4;
 mod tempfile;
 mod term;
 mod time;