diff --git a/src/sha256.c b/src/sha256.c
new file mode 100644
index 0000000..24e57b9
--- /dev/null
+++ b/src/sha256.c
@@ -0,0 +1,429 @@
+/* vi:set ts=8 sts=4 sw=4:
+ *
+ *  FIPS-180-2 compliant SHA-256 implementation
+ *  GPL by Christophe Devine.
+ *  Modified for md5deep, in public domain.
+ *  Modified For Vim, GPL(C) Mohsin Ahmed, http://www.cs.albany.edu/~mosh
+ *
+ *  Vim specific notes:
+ *  Functions exported by this file:
+ *   1. sha256_key() hashes the password to 64 bytes char string.
+ *   2. sha2_seed() generates a random header.
+ *   sha256_self_test() is implicitly called once.
+ */
+
+#include "vim.h"
+
+#ifdef FEAT_CRYPT
+
+typedef unsigned long uint32_t;
+
+typedef struct {
+  uint32_t total[2];
+  uint32_t state[8];
+  char_u   buffer[64];
+} context_sha256_T;
+
+static void sha256_starts __ARGS((context_sha256_T *ctx));
+static void sha256_process __ARGS((context_sha256_T *ctx, char_u data[64]));
+static void sha256_update __ARGS((context_sha256_T *ctx, char_u *input, uint32_t length));
+static void sha256_finish __ARGS((context_sha256_T *ctx, char_u digest[32]));
+static char *sha256_bytes __ARGS((char *buf, int buflen));
+static unsigned int get_some_time __ARGS((void));
+
+
+#define GET_UINT32(n, b, i)		    \
+{					    \
+    (n) = ( (uint32_t)(b)[(i)	 ] << 24)   \
+	| ( (uint32_t)(b)[(i) + 1] << 16)   \
+	| ( (uint32_t)(b)[(i) + 2] <<  8)   \
+	| ( (uint32_t)(b)[(i) + 3]	);  \
+}
+
+#define PUT_UINT32(n,b,i)		  \
+{					  \
+    (b)[(i)    ] = (char_u)((n) >> 24);   \
+    (b)[(i) + 1] = (char_u)((n) >> 16);   \
+    (b)[(i) + 2] = (char_u)((n) >>  8);   \
+    (b)[(i) + 3] = (char_u)((n)      );   \
+}
+
+    static void
+sha256_starts(ctx)
+    context_sha256_T *ctx;
+{
+    ctx->total[0] = 0;
+    ctx->total[1] = 0;
+
+    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;
+}
+
+    static void
+sha256_process(ctx, data)
+    context_sha256_T *ctx;
+    char_u	     data[64];
+{
+    uint32_t temp1, temp2, W[64];
+    uint32_t A, B, C, D, E, F, G, H;
+
+    GET_UINT32(W[0],  data,  0);
+    GET_UINT32(W[1],  data,  4);
+    GET_UINT32(W[2],  data,  8);
+    GET_UINT32(W[3],  data, 12);
+    GET_UINT32(W[4],  data, 16);
+    GET_UINT32(W[5],  data, 20);
+    GET_UINT32(W[6],  data, 24);
+    GET_UINT32(W[7],  data, 28);
+    GET_UINT32(W[8],  data, 32);
+    GET_UINT32(W[9],  data, 36);
+    GET_UINT32(W[10], data, 40);
+    GET_UINT32(W[11], data, 44);
+    GET_UINT32(W[12], data, 48);
+    GET_UINT32(W[13], data, 52);
+    GET_UINT32(W[14], data, 56);
+    GET_UINT32(W[15], data, 60);
+
+#define  SHR(x, n) ((x & 0xFFFFFFFF) >> n)
+#define ROTR(x, n) (SHR(x, n) | (x << (32 - n)))
+
+#define S0(x) (ROTR(x, 7) ^ ROTR(x, 18) ^  SHR(x, 3))
+#define S1(x) (ROTR(x, 17) ^ ROTR(x, 19) ^  SHR(x, 10))
+
+#define S2(x) (ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
+#define S3(x) (ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))
+
+#define F0(x, y, z) ((x & y) | (z & (x | y)))
+#define F1(x, y, z) (z ^ (x & (y ^ z)))
+
+#define R(t)				\
+(					\
+    W[t] = S1(W[t -  2]) + W[t -  7] +	\
+	   S0(W[t - 15]) + W[t - 16]	\
+)
+
+#define P(a,b,c,d,e,f,g,h,x,K)		     \
+{					     \
+    temp1 = h + S3(e) + F1(e, f, g) + K + x; \
+    temp2 = S2(a) + F0(a, b, c);	     \
+    d += temp1; h = temp1 + temp2;	     \
+}
+
+    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];
+
+    P( A, B, C, D, E, F, G, H, W[ 0], 0x428A2F98);
+    P( H, A, B, C, D, E, F, G, W[ 1], 0x71374491);
+    P( G, H, A, B, C, D, E, F, W[ 2], 0xB5C0FBCF);
+    P( F, G, H, A, B, C, D, E, W[ 3], 0xE9B5DBA5);
+    P( E, F, G, H, A, B, C, D, W[ 4], 0x3956C25B);
+    P( D, E, F, G, H, A, B, C, W[ 5], 0x59F111F1);
+    P( C, D, E, F, G, H, A, B, W[ 6], 0x923F82A4);
+    P( B, C, D, E, F, G, H, A, W[ 7], 0xAB1C5ED5);
+    P( A, B, C, D, E, F, G, H, W[ 8], 0xD807AA98);
+    P( H, A, B, C, D, E, F, G, W[ 9], 0x12835B01);
+    P( G, H, A, B, C, D, E, F, W[10], 0x243185BE);
+    P( F, G, H, A, B, C, D, E, W[11], 0x550C7DC3);
+    P( E, F, G, H, A, B, C, D, W[12], 0x72BE5D74);
+    P( D, E, F, G, H, A, B, C, W[13], 0x80DEB1FE);
+    P( C, D, E, F, G, H, A, B, W[14], 0x9BDC06A7);
+    P( B, C, D, E, F, G, H, A, W[15], 0xC19BF174);
+    P( A, B, C, D, E, F, G, H, R(16), 0xE49B69C1);
+    P( H, A, B, C, D, E, F, G, R(17), 0xEFBE4786);
+    P( G, H, A, B, C, D, E, F, R(18), 0x0FC19DC6);
+    P( F, G, H, A, B, C, D, E, R(19), 0x240CA1CC);
+    P( E, F, G, H, A, B, C, D, R(20), 0x2DE92C6F);
+    P( D, E, F, G, H, A, B, C, R(21), 0x4A7484AA);
+    P( C, D, E, F, G, H, A, B, R(22), 0x5CB0A9DC);
+    P( B, C, D, E, F, G, H, A, R(23), 0x76F988DA);
+    P( A, B, C, D, E, F, G, H, R(24), 0x983E5152);
+    P( H, A, B, C, D, E, F, G, R(25), 0xA831C66D);
+    P( G, H, A, B, C, D, E, F, R(26), 0xB00327C8);
+    P( F, G, H, A, B, C, D, E, R(27), 0xBF597FC7);
+    P( E, F, G, H, A, B, C, D, R(28), 0xC6E00BF3);
+    P( D, E, F, G, H, A, B, C, R(29), 0xD5A79147);
+    P( C, D, E, F, G, H, A, B, R(30), 0x06CA6351);
+    P( B, C, D, E, F, G, H, A, R(31), 0x14292967);
+    P( A, B, C, D, E, F, G, H, R(32), 0x27B70A85);
+    P( H, A, B, C, D, E, F, G, R(33), 0x2E1B2138);
+    P( G, H, A, B, C, D, E, F, R(34), 0x4D2C6DFC);
+    P( F, G, H, A, B, C, D, E, R(35), 0x53380D13);
+    P( E, F, G, H, A, B, C, D, R(36), 0x650A7354);
+    P( D, E, F, G, H, A, B, C, R(37), 0x766A0ABB);
+    P( C, D, E, F, G, H, A, B, R(38), 0x81C2C92E);
+    P( B, C, D, E, F, G, H, A, R(39), 0x92722C85);
+    P( A, B, C, D, E, F, G, H, R(40), 0xA2BFE8A1);
+    P( H, A, B, C, D, E, F, G, R(41), 0xA81A664B);
+    P( G, H, A, B, C, D, E, F, R(42), 0xC24B8B70);
+    P( F, G, H, A, B, C, D, E, R(43), 0xC76C51A3);
+    P( E, F, G, H, A, B, C, D, R(44), 0xD192E819);
+    P( D, E, F, G, H, A, B, C, R(45), 0xD6990624);
+    P( C, D, E, F, G, H, A, B, R(46), 0xF40E3585);
+    P( B, C, D, E, F, G, H, A, R(47), 0x106AA070);
+    P( A, B, C, D, E, F, G, H, R(48), 0x19A4C116);
+    P( H, A, B, C, D, E, F, G, R(49), 0x1E376C08);
+    P( G, H, A, B, C, D, E, F, R(50), 0x2748774C);
+    P( F, G, H, A, B, C, D, E, R(51), 0x34B0BCB5);
+    P( E, F, G, H, A, B, C, D, R(52), 0x391C0CB3);
+    P( D, E, F, G, H, A, B, C, R(53), 0x4ED8AA4A);
+    P( C, D, E, F, G, H, A, B, R(54), 0x5B9CCA4F);
+    P( B, C, D, E, F, G, H, A, R(55), 0x682E6FF3);
+    P( A, B, C, D, E, F, G, H, R(56), 0x748F82EE);
+    P( H, A, B, C, D, E, F, G, R(57), 0x78A5636F);
+    P( G, H, A, B, C, D, E, F, R(58), 0x84C87814);
+    P( F, G, H, A, B, C, D, E, R(59), 0x8CC70208);
+    P( E, F, G, H, A, B, C, D, R(60), 0x90BEFFFA);
+    P( D, E, F, G, H, A, B, C, R(61), 0xA4506CEB);
+    P( C, D, E, F, G, H, A, B, R(62), 0xBEF9A3F7);
+    P( B, C, D, E, F, G, H, A, R(63), 0xC67178F2);
+
+    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 void
+sha256_update(ctx, input, length)
+    context_sha256_T *ctx;
+    char_u	     *input;
+    uint32_t	     length;
+{
+    uint32_t left, fill;
+
+    if (length == 0)
+	return;
+
+    left = ctx->total[0] & 0x3F;
+    fill = 64 - left;
+
+    ctx->total[0] += length;
+    ctx->total[0] &= 0xFFFFFFFF;
+
+    if (ctx->total[0] < length)
+	ctx->total[1]++;
+
+    if (left && length >= fill)
+    {
+	memcpy((void *)(ctx->buffer + left), (void *)input, fill);
+	sha256_process(ctx, ctx->buffer);
+	length -= fill;
+	input  += fill;
+	left = 0;
+    }
+
+    while (length >= 64)
+    {
+	sha256_process(ctx, input);
+	length -= 64;
+	input  += 64;
+    }
+
+    if (length)
+	memcpy((void *)(ctx->buffer + left), (void *)input, length);
+}
+
+static char_u sha256_padding[64] = {
+    0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+};
+
+    static void
+sha256_finish(ctx, digest)
+    context_sha256_T *ctx;
+    char_u           digest[32];
+{
+    uint32_t last, padn;
+    uint32_t high, low;
+    char_u   msglen[8];
+
+    high = (ctx->total[0] >> 29) | (ctx->total[1] <<  3);
+    low  = (ctx->total[0] <<  3);
+
+    PUT_UINT32(high, msglen, 0);
+    PUT_UINT32(low,  msglen, 4);
+
+    last = ctx->total[0] & 0x3F;
+    padn = (last < 56) ? (56 - last) : (120 - last);
+
+    sha256_update(ctx, sha256_padding, padn);
+    sha256_update(ctx, msglen, 8);
+
+    PUT_UINT32(ctx->state[0], digest,  0);
+    PUT_UINT32(ctx->state[1], digest,  4);
+    PUT_UINT32(ctx->state[2], digest,  8);
+    PUT_UINT32(ctx->state[3], digest, 12);
+    PUT_UINT32(ctx->state[4], digest, 16);
+    PUT_UINT32(ctx->state[5], digest, 20);
+    PUT_UINT32(ctx->state[6], digest, 24);
+    PUT_UINT32(ctx->state[7], digest, 28);
+}
+
+    static char *
+sha256_bytes(buf, buflen)
+    char *buf;
+    int  buflen;
+{
+    char_u	     sha256sum[32];
+    static char      hexit[65];
+    int		     j;
+    context_sha256_T ctx;
+
+    sha256_self_test();
+
+    sha256_starts(&ctx);
+    sha256_update(&ctx, (char_u *)buf, buflen);
+    sha256_finish(&ctx, sha256sum);
+    for (j = 0; j < 32; j++)
+	sprintf(hexit + j * 2, "%02x", sha256sum[j]);
+    hexit[sizeof(hexit) - 1] = '\0';
+    return hexit;
+}
+
+/*
+ * Returns sha256(buf) as 64 hex chars.
+ */
+    char *
+sha256_key(buf)
+    char *buf;
+{
+    static char *hexit = 0;
+    int		buflen;
+
+    /* No passwd means don't encrypt */
+    if (buf == NULL || *buf == NUL)
+	return "";
+
+    /* if password is "0", reuse previous hash, for user convienience. */
+    if (!strcmp(buf, "0") && hexit)
+	return hexit;
+
+    buflen = strlen(buf);
+    hexit = sha256_bytes(buf, buflen);
+    return hexit;
+}
+
+/*
+ * These are the standard FIPS-180-2 test vectors
+ */
+
+static char *sha_self_test_msg[] = {
+    "abc",
+    "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
+    NULL
+};
+
+static char *sha_self_test_vector[] = {
+    "ba7816bf8f01cfea414140de5dae2223" \
+    "b00361a396177a9cb410ff61f20015ad",
+    "248d6a61d20638b8e5c026930c3e6039" \
+    "a33ce45964ff2167f6ecedd419db06c1",
+    "cdc76e5c9914fb9281a1c7e284d73e67" \
+    "f1809a48a497200e046d39ccc7112cd0"
+};
+
+/*
+ * Perform a test on the SHA256 algorithm.
+ * Return FAIL or OK.
+ */
+    int
+sha256_self_test()
+{
+    int		     i, j;
+    char	     output[65];
+    context_sha256_T ctx;
+    char_u	     buf[1000];
+    char_u	     sha256sum[32];
+    static int	     failures = 0;
+    char	     *hexit;
+    static int	     sha256_self_tested = 0;
+
+    if (sha256_self_tested > 0)
+	return failures > 0 ? FAIL : OK;
+    sha256_self_tested = 1;
+
+    for (i = 0; i < 3; i++)
+    {
+	if (i < 2)
+	{
+	    hexit = sha256_bytes(sha_self_test_msg[i],
+						strlen(sha_self_test_msg[i]));
+	    strcpy(output, hexit);
+	}
+	else
+	{
+	    sha256_starts(&ctx);
+	    memset(buf, 'a', 1000);
+	    for (j = 0; j < 1000; j++)
+		sha256_update(&ctx, (char_u *)buf, 1000);
+	    sha256_finish(&ctx, sha256sum);
+	    for (j = 0; j < 32; j++)
+		sprintf(output + j * 2, "%02x", sha256sum[j]);
+	}
+	if (memcmp(output, sha_self_test_vector[i], 64))
+	{
+	    failures++;
+	    output[sizeof(output) - 1] = '\0';
+	    /* printf("sha256_self_test %d failed %s\n", i, output); */
+	}
+    }
+    return failures > 0 ? FAIL : OK;
+}
+
+    static unsigned int
+get_some_time()
+{
+#ifdef HAVE_GETTIMEOFDAY
+    struct timeval tv;
+
+    /* Using usec makes it less predictable. */
+    gettimeofday(&tv, NULL);
+    return (unsigned int)(tv.tv_sec + tv.tv_usec);
+#else
+    return (unsigned int)time(NULL);
+#endif
+}
+
+/*
+ * set header = sha2_seed(random_data);
+ */
+    void
+sha2_seed(header, header_len)
+    char_u header[];
+    int    header_len;
+{
+    int		     i;
+    static char_u    random_data[1000];
+    char_u	     sha256sum[32];
+    context_sha256_T ctx;
+    srand(get_some_time());
+
+    for (i = 0; i < (int)sizeof(random_data) - 1; i++)
+	random_data[i] = (char_u)((get_some_time() ^ rand()) & 0xff);
+    sha256_starts(&ctx);
+    sha256_update(&ctx, (char_u *)random_data, sizeof(random_data));
+    sha256_finish(&ctx, sha256sum);
+
+    for (i = 0; i < header_len; i++)
+	header[i] = sha256sum[i % sizeof(sha256sum)];
+}
+
+#endif /* FEAT_CRYPT */