diff --git a/libmincrypt/sha256.c b/libmincrypt/sha256.c
new file mode 100644
index 0000000..eb6e308
--- /dev/null
+++ b/libmincrypt/sha256.c
@@ -0,0 +1,184 @@
+/* sha256.c
+**
+** Copyright 2013, The Android Open Source Project
+**
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+**     * Redistributions of source code must retain the above copyright
+**       notice, this list of conditions and the following disclaimer.
+**     * Redistributions in binary form must reproduce the above copyright
+**       notice, this list of conditions and the following disclaimer in the
+**       documentation and/or other materials provided with the distribution.
+**     * Neither the name of Google Inc. nor the names of its contributors may
+**       be used to endorse or promote products derived from this software
+**       without specific prior written permission.
+**
+** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR
+** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+// Optimized for minimal code size.
+
+#include "mincrypt/sha256.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#define ror(value, bits) (((value) >> (bits)) | ((value) << (32 - (bits))))
+#define shr(value, bits) ((value) >> (bits))
+
+static const uint32_t K[64] = {
+    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
+    0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
+    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
+    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
+    0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
+    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
+    0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
+    0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
+    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2 };
+
+static void SHA256_Transform(SHA256_CTX* ctx) {
+    uint32_t W[64];
+    uint32_t A, B, C, D, E, F, G, H;
+    uint8_t* p = ctx->buf;
+    int t;
+
+    for(t = 0; t < 16; ++t) {
+        uint32_t tmp =  *p++ << 24;
+        tmp |= *p++ << 16;
+        tmp |= *p++ << 8;
+        tmp |= *p++;
+        W[t] = tmp;
+    }
+
+    for(; t < 64; t++) {
+        uint32_t s0 = ror(W[t-15], 7) ^ ror(W[t-15], 18) ^ shr(W[t-15], 3);
+        uint32_t s1 = ror(W[t-2], 17) ^ ror(W[t-2], 19) ^ shr(W[t-2], 10);
+        W[t] = W[t-16] + s0 + W[t-7] + s1;
+    }
+
+    A = ctx->state[0];
+    B = ctx->state[1];
+    C = ctx->state[2];
+    D = ctx->state[3];
+    E = ctx->state[4];
+    F = ctx->state[5];
+    G = ctx->state[6];
+    H = ctx->state[7];
+
+    for(t = 0; t < 64; t++) {
+        uint32_t s0 = ror(A, 2) ^ ror(A, 13) ^ ror(A, 22);
+        uint32_t maj = (A & B) ^ (A & C) ^ (B & C);
+        uint32_t t2 = s0 + maj;
+        uint32_t s1 = ror(E, 6) ^ ror(E, 11) ^ ror(E, 25);
+        uint32_t ch = (E & F) ^ ((~E) & G);
+        uint32_t t1 = H + s1 + ch + K[t] + W[t];
+
+        H = G;
+        G = F;
+        F = E;
+        E = D + t1;
+        D = C;
+        C = B;
+        B = A;
+        A = t1 + t2;
+    }
+
+    ctx->state[0] += A;
+    ctx->state[1] += B;
+    ctx->state[2] += C;
+    ctx->state[3] += D;
+    ctx->state[4] += E;
+    ctx->state[5] += F;
+    ctx->state[6] += G;
+    ctx->state[7] += H;
+}
+
+static const HASH_VTAB SHA256_VTAB = {
+    SHA256_init,
+    SHA256_update,
+    SHA256_final,
+    SHA256_hash,
+    SHA256_DIGEST_SIZE
+};
+
+void SHA256_init(SHA256_CTX* ctx) {
+    ctx->f = &SHA256_VTAB;
+    ctx->state[0] = 0x6a09e667;
+    ctx->state[1] = 0xbb67ae85;
+    ctx->state[2] = 0x3c6ef372;
+    ctx->state[3] = 0xa54ff53a;
+    ctx->state[4] = 0x510e527f;
+    ctx->state[5] = 0x9b05688c;
+    ctx->state[6] = 0x1f83d9ab;
+    ctx->state[7] = 0x5be0cd19;
+    ctx->count = 0;
+}
+
+
+void SHA256_update(SHA256_CTX* ctx, const void* data, int len) {
+    int i = (int) (ctx->count & 63);
+    const uint8_t* p = (const uint8_t*)data;
+
+    ctx->count += len;
+
+    while (len--) {
+        ctx->buf[i++] = *p++;
+        if (i == 64) {
+            SHA256_Transform(ctx);
+            i = 0;
+        }
+    }
+}
+
+
+const uint8_t* SHA256_final(SHA256_CTX* ctx) {
+    uint8_t *p = ctx->buf;
+    uint64_t cnt = ctx->count * 8;
+    int i;
+
+    SHA256_update(ctx, (uint8_t*)"\x80", 1);
+    while ((ctx->count & 63) != 56) {
+        SHA256_update(ctx, (uint8_t*)"\0", 1);
+    }
+    for (i = 0; i < 8; ++i) {
+        uint8_t tmp = (uint8_t) (cnt >> ((7 - i) * 8));
+        SHA256_update(ctx, &tmp, 1);
+    }
+
+    for (i = 0; i < 8; i++) {
+        uint32_t tmp = ctx->state[i];
+        *p++ = tmp >> 24;
+        *p++ = tmp >> 16;
+        *p++ = tmp >> 8;
+        *p++ = tmp >> 0;
+    }
+
+    return ctx->buf;
+}
+
+/* Convenience function */
+const uint8_t* SHA256_hash(const void* data, int len, uint8_t* digest) {
+    SHA256_CTX ctx;
+    SHA256_init(&ctx);
+    SHA256_update(&ctx, data, len);
+    memcpy(digest, SHA256_final(&ctx), SHA256_DIGEST_SIZE);
+    return digest;
+}