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-rw-r--r--libkeccak_cshake_initialise.c275
1 files changed, 275 insertions, 0 deletions
diff --git a/libkeccak_cshake_initialise.c b/libkeccak_cshake_initialise.c
new file mode 100644
index 0000000..dd47fc6
--- /dev/null
+++ b/libkeccak_cshake_initialise.c
@@ -0,0 +1,275 @@
+#include <stdio.h>
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Encode a number in big-endian with a size prefix
+ *
+ * @param state The hashing state the feed the number to
+ * @param buf Buffer that is at least `byterate` bytes large
+ * @param byterate The byterate of the hashing algorithm
+ * @param value The number to send to the hashing sponge
+ * @param off Current offset in `buf`
+ * @return New offset in `buf`
+ */
+static size_t
+encode_left(struct libkeccak_state *restrict state, uint8_t *restrict buf, size_t byterate, size_t value, size_t off)
+{
+ size_t x, n, j, i = off;
+
+ for (x = value, n = 0; x; x >>= 8)
+ n += 1;
+ if (!n)
+ n = 1;
+ buf[i++] = (uint8_t)n;
+ if (i == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ i = 0;
+ }
+
+ for (j = 0; j < n;) {
+ buf[i++] = (uint8_t)(value >> ((n - ++j) << 3));
+ if (i == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ i = 0;
+ }
+ }
+
+ return i;
+}
+
+
+/**
+ * Encode a number in big-endian with a size prefix
+ *
+ * @param state The hashing state the feed the number to
+ * @param buf Buffer that is at least `byterate` bytes large
+ * @param byterate The byterate of the hashing algorithm
+ * @param value The number to send to the hashing sponge
+ * @param off Current offset in `buf`
+ * @param bitoff The number of bits to shift the encoded message left
+ * @return New offset in `buf`
+ */
+static size_t
+encode_left_shifted(struct libkeccak_state *restrict state, uint8_t *restrict buf,
+ size_t byterate, size_t value, size_t off, size_t bitoff)
+{
+ size_t x, n, j, i = off;
+ uint16_t v;
+
+ for (x = value, n = 0; x; x >>= 8)
+ n += 1;
+ if (!n)
+ n = 1;
+ v = (uint16_t)((n & 255UL) << bitoff);
+ buf[i++] |= (uint8_t)v;
+ if (i == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ i = 0;
+ }
+ buf[i] = (uint8_t)(n >> 8);
+
+ for (j = 0; j < n;) {
+ v = (uint16_t)(((value >> ((n - ++j) << 3)) & 255UL) << bitoff);
+ buf[i++] |= (uint8_t)v;
+ if (i == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ i = 0;
+ }
+ buf[i] = (uint8_t)(v >> 8);
+ }
+
+ return i;
+}
+
+
+/**
+ * Feed text to the sponge
+ *
+ * @param state The hashing state tofeed
+ * @param buf Buffer that is at least `byterate` bytes large
+ * @param text Text to feed the sponge
+ * @param bytes The number of whole bytes in `text`
+ * @param bits The number of bits at the end of `text`
+ * that does not make up a whole byte
+ * @param suffix Bit-string (encoded with ASCII 0/1 digits)
+ * of additional bytes after `text`
+ * @param off The current byte offset in `buf`
+ * @param byterate The byterate of the hashing algorithm
+ * @param bitoffp Output parameter for the non-whole
+ * byte bit-offset (current must be 0)
+ * @return The new byte offset in `buf`
+ */
+static size_t
+feed_text(struct libkeccak_state *restrict state, uint8_t *restrict buf, const uint8_t *restrict text, size_t bytes,
+ size_t bits, const char *restrict suffix, size_t off, size_t byterate, size_t *restrict bitoffp)
+{
+ size_t n, bitoff;
+
+ if (off) {
+ n = bytes < byterate - off ? bytes : byterate - off;
+ memcpy(&buf[off], text, n);
+ off += n;
+ if (off == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ off = 0;
+ }
+ text = &text[n];
+ bytes -= n;
+ }
+ if (bytes) {
+ n = bytes;
+ n -= bytes %= byterate;
+ libkeccak_zerocopy_update(state, text, n);
+ text = &text[n];
+ }
+ memcpy(&buf[off], text, bytes + !!bits);
+ off += bytes;
+ bitoff = bits;
+ if (!bitoff)
+ buf[off] = 0;
+ for (; *suffix; suffix++) {
+ if (*suffix == '1')
+ buf[off] |= (uint8_t)(1 << bitoff);
+ if (++bitoff == 8) {
+ if (++off == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ off = 0;
+ }
+ bitoff = 0;
+ buf[off] = 0;
+ }
+ }
+
+ *bitoffp = bitoff;
+ return off;
+}
+
+
+/**
+ * Feed text to the sponge
+ *
+ * @param state The hashing state tofeed
+ * @param buf Buffer that is at least `byterate` bytes large
+ * @param text Text to feed the sponge
+ * @param bytes The number of whole bytes in `text`
+ * @param bits The number of bits at the end of `text`
+ * that does not make up a whole byte
+ * @param suffix Bit-string (encoded with ASCII 0/1 digits)
+ * of additional bytes after `text`
+ * @param off The current byte offset in `buf`
+ * @param byterate The byterate of the hashing algorithm
+ * @param bitoffp Pointer to the non-whole byte bit-offset,
+ * shall be the current (non-zero) bit-offset
+ * upon entry and will be set to the new
+ * bit-offset on return
+ * @return The new byte offset in `buf`
+ */
+static size_t
+feed_text_shifted(struct libkeccak_state *restrict state, uint8_t *restrict buf, const uint8_t *restrict text, size_t bytes,
+ size_t bits, const char *restrict suffix, size_t off, size_t byterate, size_t *restrict bitoffp)
+{
+ size_t i, bitoff = *bitoffp;
+ uint16_t v;
+
+ for (i = 0; i < bytes; i++) {
+ v = (uint16_t)((uint16_t)text[i] << bitoff);
+ buf[off] |= (uint8_t)v;
+ if (++off == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ off = 0;
+ }
+ buf[off] = (uint8_t)(v >> 8);
+ }
+ if (bits) {
+ v = (uint16_t)((uint16_t)text[bytes] << bitoff);
+ buf[off] |= (uint8_t)v;
+ bitoff += bits;
+ if (bitoff >= 8) {
+ if (++off == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ off = 0;
+ }
+ bitoff &= 7;
+ buf[off] = (uint8_t)(v >> 8);
+ }
+ }
+ if (!bitoff)
+ buf[off] = 0;
+ for (; *suffix; suffix++) {
+ if (*suffix == '1')
+ buf[off] |= (uint8_t)(1 << bitoff);
+ if (++bitoff == 8) {
+ if (++off == byterate) {
+ libkeccak_zerocopy_update(state, buf, byterate);
+ off = 0;
+ }
+ bitoff = 0;
+ buf[off] = 0;
+ }
+ }
+
+ *bitoffp = bitoff;
+ return off;
+}
+
+
+/**
+ * Create and absorb the initialisation blocks for cSHAKE hashing
+ *
+ * @param state The hashing state
+ * @param n_text Function name-string
+ * @param n_len Byte-length of `n_text` (only whole byte)
+ * @param n_bits Bit-length of `n_text`, minus `n_len * 8`
+ * @param n_suffix Bit-string, represented by a NUL-terminated
+ * string of '1':s and '0's:, making up the part
+ * after `n_text` of the function-name bit-string;
+ * `NULL` is treated as the empty string
+ * @param s_text Customisation-string
+ * @param s_len Byte-length of `s_text` (only whole byte)
+ * @param s_bits Bit-length of `s_text`, minus `s_len * 8`
+ * @param s_suffix Bit-string, represented by a NUL-terminated
+ * string of '1':s and '0's:, making up the part
+ * after `s_text` of the customisation bit-string;
+ * `NULL` is treated as the empty string
+ */
+void
+libkeccak_cshake_initialise(struct libkeccak_state *restrict state,
+ const void *n_text, size_t n_len, size_t n_bits, const char *n_suffix,
+ const void *s_text, size_t s_len, size_t s_bits, const char *s_suffix)
+{
+ size_t off = 0, bitoff, byterate = (size_t)state->r >> 3;
+
+ if (!n_suffix)
+ n_suffix = "";
+ if (!s_suffix)
+ s_suffix = "";
+
+ if (!n_len && !s_len && !n_bits && !s_bits && !*n_suffix && !*s_suffix)
+ return;
+
+ n_len += n_bits >> 3;
+ s_len += s_bits >> 3;
+ n_bits &= 7;
+ s_bits &= 7;
+
+ off = encode_left(state, state->M, byterate, byterate, off);
+ off = encode_left(state, state->M, byterate, (n_len << 3) + n_bits + strlen(n_suffix), off);
+ off = feed_text(state, state->M, n_text, n_len, n_bits, n_suffix, off, byterate, &bitoff);
+
+ if (!bitoff) {
+ off = encode_left(state, state->M, byterate, (s_len << 3) + s_bits + strlen(s_suffix), off);
+ off = feed_text(state, state->M, s_text, s_len, s_bits, s_suffix, off, byterate, &bitoff);
+ } else {
+ off = encode_left_shifted(state, state->M, byterate, (s_len << 3) + s_bits + strlen(s_suffix), off, bitoff);
+ off = feed_text_shifted(state, state->M, s_text, s_len, s_bits, s_suffix, off, byterate, &bitoff);
+ }
+
+ if (bitoff)
+ off++;
+ if (off) {
+ memset(&state->M[off], 0, byterate - off);
+ libkeccak_zerocopy_update(state, state->M, byterate);
+ }
+}
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