cryptopals_c

commit 9d9894dbd16f23bc6ca3e5933f1fb93f65f781fa
parent 2086d07fcc3fcf69929a22790456c54b98fe2004
Author: superpozycja <anna@superpozycja.net>
Date:   Tue, 25 Feb 2025 20:19:18 +0100

lib/block: add ecb mode without padding

Diffstat:
A
lib/block.c
 | 
67
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
lib/block.h
 | 
16
++++++++++++++++

2 files changed, 83 insertions(+), 0 deletions(-)
diff --git a/lib/block.c b/lib/block.c
@@ -0,0 +1,67 @@
+#include "block.h"
+
+
+static int split_to_chunks(ba *src, uint16_t block_size, uint16_t chunks_n,
+                           ba *dest[chunks_n])
+{
+	int i;
+
+	for (i = 0; i < chunks_n; i++)
+		dest[i] = ba_alloc(block_size);
+
+	i = 0;
+	while (i < src->len)
+		dest[(i)/block_size]->val[(i++)%block_size] = src->val[i];
+
+	while (i < block_size * chunks_n)
+		dest[i/chunks_n]->val[(i++)%chunks_n] = 0;
+
+	return 0;
+}
+
+static int unsplit_from_chunks(ba **dest, uint16_t block_size, uint16_t chunks_n,
+                               ba *src[chunks_n])
+{
+	int ct_size;
+	int i;
+
+	ct_size = block_size * chunks_n;
+	*dest = ba_alloc(ct_size);
+
+	i = 0;
+	while (i < ct_size)
+		(*dest)->val[i++] = src[(i)/block_size]->val[(i)%block_size];
+
+	return 0;
+}
+
+int encrypt_ecb(ba *plaintext, ba *key, ba **ciphertext, uint16_t block_size,
+                int (* encrypt) (ba *, ba *, ba **))
+{
+	uint16_t chunks_n = (plaintext->len / block_size) +
+	                    (plaintext->len % block_size == 1);
+	ba *ct_chunks[chunks_n];
+	ba *chunks[chunks_n];
+
+	split_to_chunks(plaintext, block_size, chunks_n, chunks);
+	for (int i = 0; i < chunks_n; i++) {
+		ct_chunks[i] = ba_alloc(block_size);
+
+		encrypt(chunks[i], key, &ct_chunks[i]);
+		ba_free(chunks[i]);
+	}
+
+	unsplit_from_chunks(ciphertext, block_size, chunks_n, ct_chunks);
+
+	for (int i = 0; i < chunks_n; i++)
+		ba_free(ct_chunks[i]);
+
+	return 0;
+}
+
+int decrypt_ecb(ba *ciphertext, ba *key, ba **plaintext, uint16_t block_size,
+                int (* decrypt) (ba *, ba *, ba **))
+{
+	/* this is symmetric */
+	return encrypt_ecb(ciphertext, key, plaintext, block_size, decrypt);
+}
diff --git a/lib/block.h b/lib/block.h
@@ -0,0 +1,16 @@
+#ifndef BLOCK_H_1e491544
+#define BLOCK_H_1e491544
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+#include "ba.h"
+
+int encrypt_ecb(ba *plaintext, ba *key, ba **ciphertext, uint16_t block_size,
+                int (* encrypt) (ba *, ba *, ba **));
+
+int decrypt_ecb(ba *ciphertext, ba *key, ba **plaintext, uint16_t block_size,
+                int (* decrypt) (ba *, ba *, ba **));
+
+#endif