commit 2f924e29a9c2326b9332a71b6b8f15a2472d396d
parent ce655d05afe60a05c5a959e3562ef0d6255c40a5
Author: William Casarin <jb55@jb55.com>
Date: Sat, 25 May 2019 06:05:36 -0700
descriptor checksums working
Diffstat:
4 files changed, 104 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile
@@ -15,6 +15,7 @@ OBJS += compiler.o
OBJS += ec.o
OBJS += hash.o
OBJS += base58.o
+OBJS += descriptor.o
SRCS=$(OBJS:.o=.c)
diff --git a/check.c b/check.c
@@ -1,8 +1,19 @@
#include "bip32.h"
+#include "descriptor.h"
#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+
+#define streq(a, b) strcmp(a, b) == 0
int main()
{
+ char checksum[9];
+ const char desc[] = "combo(xpub661MyMwAqRbcEzDwwjzJhBnXBZpv9hdqY2JYRUtwzEZU6grFRhWkXx9c3HJ4EKR1Nvdwf5U3VoekstoKSKjfcJYhRrhMYeEzZzu2h7uZAQX/1/*)";
+ const char *desc_check = "j38hxvh0";
+ int ok = descriptor_checksum(desc, sizeof(desc)-1, checksum, sizeof(checksum));
+ assert(ok);
+ assert(streq(checksum, desc_check));
return 0;
}
diff --git a/descriptor.c b/descriptor.c
@@ -0,0 +1,83 @@
+
+#include "short_types.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+static const char CHECKSUM_CHARSET[] = "qpzry9x8gf2tvdw0s3jn54khce6mua7l";
+
+static const char INPUT_CHARSET[] =
+ "0123456789()[],'/*abcdefgh@:$%{}"
+ "IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~"
+ "ijklmnopqrstuvwxyzABCDEFGH`#\"\\ ";
+
+static inline int charset_find(char ch) {
+ for (size_t i = 0; i < sizeof(INPUT_CHARSET); i++) {
+ if (INPUT_CHARSET[i] == ch)
+ return i;
+ }
+ return -1;
+}
+
+static u64 polymod(u64 c, int val)
+{
+ u8 c0 = c >> 35;
+ c = ((c & 0x7ffffffff) << 5) ^ val;
+ if (c0 & 1) c ^= 0xf5dee51989;
+ if (c0 & 2) c ^= 0xa9fdca3312;
+ if (c0 & 4) c ^= 0x1bab10e32d;
+ if (c0 & 8) c ^= 0x3706b1677a;
+ if (c0 & 16) c ^= 0x644d626ffd;
+ return c;
+}
+
+
+int descriptor_checksum(const char *descriptor, int desc_size, char *checksum,
+ int checksum_capacity)
+{
+ if (checksum_capacity < 8+1)
+ return 0;
+
+ checksum[0] = 0;
+
+ int j;
+ u64 c = 1;
+ int cls = 0;
+ int clscount = 0;
+
+ for (int i = 0; i < desc_size; i++) {
+ char ch = descriptor[i];
+ int pos = charset_find(ch);
+ if (pos == -1) {
+ checksum[0] = 0;
+ return 0;
+ }
+ // Emit a symbol for the position inside the group, for every character.
+ c = polymod(c, pos & 31);
+
+ // Accumulate the group numbers
+ cls = cls * 3 + (pos >> 5);
+
+ if (++clscount == 3) {
+ c = polymod(c, cls);
+ cls = 0;
+ clscount = 0;
+ }
+ }
+
+ if (clscount > 0)
+ c = polymod(c, cls);
+
+ // Shift further to determine the checksum.
+ for (j = 0; j < 8; ++j)
+ c = polymod(c, 0);
+
+ // Prevent appending zeroes from not affecting the checksum.
+ c ^= 1;
+
+ for (j = 0; j < 8; ++j)
+ checksum[j] = CHECKSUM_CHARSET[(c >> (5 * (7 - j))) & 31];
+
+ checksum[8] = 0;
+
+ return 8;
+}
diff --git a/descriptor.h b/descriptor.h
@@ -0,0 +1,9 @@
+
+#ifndef DESCRIPTOR_H
+#define DESCRIPTOR_H
+
+
+int descriptor_checksum(const char *descriptor, int desc_size, char *checksum,
+ int checksum_capacity);
+
+#endif /* DESCRIPTOR_H */
