cryptopals_c

commit d59e0ba78af694145bd37963e8ee7397182d7080
Author: anna <anna@brokenlove.online>
Date:   Thu, 21 Mar 2024 23:27:47 +0100

initial commit

Diffstat:
A
.gitignore
 | 
2
++
A
README.md
 | 
3
+++
A
s1/build.sh
 | 
6
++++++
A
s1/c1.c
 | 
47
+++++++++++++++++++++++++++++++++++++++++++++++

4 files changed, 58 insertions(+), 0 deletions(-)
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1,2 @@
+*.swp
+bin
diff --git a/README.md b/README.md
@@ -0,0 +1,3 @@
+# cryptopals in c
+
+cryptopals in c
diff --git a/s1/build.sh b/s1/build.sh
@@ -0,0 +1,6 @@
+#!/bin/sh
+
+for filename in *.c; do
+    echo "compiling $filename"
+    cc -o "bin/$(basename $filename .c)" $filename
+done
diff --git a/s1/c1.c b/s1/c1.c
@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+static int hex_to_base64(const char* hex, char** b64)
+{
+    const char b64table[] =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+    int length = strlen(hex);
+    int block_count = length / 6;
+    int res_length = block_count*4;
+    int leftover_length = length % 6;
+    if(leftover_length%2 == 1) {
+        fprintf(stderr, "bad sequence length\n");
+        return -1;
+    }
+
+    char * res = (char*)(malloc(sizeof(char)*res_length+2));
+
+    for(int i = 0; i < block_count+(leftover_length != 0); i++) {
+        int end_ix = i < block_count ? 6 : leftover_length;
+        char block[6+1];
+        memcpy(block, hex+(6*i), end_ix);
+        block[end_ix] = '\0';
+        
+        int block_hex = strtol(block, NULL, 16);
+        block_hex <<= 4*(6-end_ix);
+        
+        for(int j = 0; j < 4; j++) {
+            char b64 = b64table[(block_hex >> 6*(3-j))& 0x3f];
+            res[4*i+j] = j <= end_ix/2 ? b64 : '=';
+        }
+    }
+    *b64 = res;
+    return 0;
+}
+
+int main(int argc, char* argv[]) 
+{
+    char* b64;
+    int ret = hex_to_base64(argv[1], &b64);
+    if(ret == 0) {
+        printf("%s\n", b64);
+    }
+    return 0;
+}