Start AES

2 files changed, 95 insertions, 0 deletions

diff --git a/aes.cpp b/aes.cpp
new file mode 100644
index 0000000..13659e6
--- /dev/null
+++ b/aes.cpp
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+#include <cstring>
+#include <cassert>
+#include "aes.h"
+
+using namespace std;
+
+namespace AES{
+
+	//http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
+
+	void subWord(uint8_t *word);
+
+	void keyExpand(uint8_t *keysched,const uint8_t *key,int keylen,int numrounds);
+
+	void addRoundKey(uint8_t *state,const uint8_t *roundkey);
+
+	void subBytes(uint8_t *state){
+		subWord(state);
+		subWord(state+4);
+		subWord(state+8);
+		subWord(state+12);
+	}
+
+	void shiftRows(uint8_t *state);
+
+	void mixColumns(uint8_t *state);
+
+
+	void encryptBlock(uint8_t *state,const uint8_t *key,const uint8_t *data,int keylen,int numrounds){
+		uint8_t keysched[16*(numrounds+1)];
+		keyExpand(keysched,key,keylen,numrounds);
+		memcpy(state,data,16);
+
+		addRoundKey(state,keysched);
+		for(int round=0;round<numrounds-1;round++){
+			subBytes(state);
+			shiftRows(state);
+			mixColumns(state);
+			addRoundKey(state,keysched+16*(round+1));
+		}
+		subBytes(state);
+		shiftRows(state);
+		addRoundKey(state,keysched+16*numrounds);
+	}
+
+	string encrypt(const string &key,const string &data,int numrounds){
+		int sz=data.size();
+		if(sz==0)return {};
+		int blocks=sz/16;
+		int padding=sz%16==0?16:16-sz%16;
+		string res;
+		assert((sz+padding)%16==0);
+		res.reserve(sz+padding);
+		uint8_t buf[16];
+		for(int i=0;i<blocks;i++){
+			encryptBlock(buf,(const uint8_t*)key.data(),(const uint8_t*)data.data()+16*i,key.size(),numrounds);
+			res.insert(res.size(),(char*)buf,16);
+		}
+		uint8_t inbuf[16];
+		if(padding<16)memcpy(inbuf,data.data()+16*blocks,16-padding);
+		memset(inbuf+16-padding,padding,padding);
+		encryptBlock(buf,(const uint8_t*)key.data(),inbuf,key.size(),numrounds);
+		res.insert(res.size(),(char*)buf,16);
+		return res;
+	}
+
+	string decrypt(const string &key,const string &data,int numrounds);
+
+	string encrypt(const string &key,const string &data,Algorithm algo){
+		assert(key.size()==4+2*algo);
+		return encrypt(key,data,10+2*algo);
+	}
+
+	string decrypt(const string &key,const string &data,Algorithm algo)/*{
+		assert(key.size()==4+2*algo);
+		return decrypt(key,data,10+2*algo);
+	}*/;
+
+}
diff --git a/aes.h b/aes.h
new file mode 100644
index 0000000..012c9ed
--- /dev/null
+++ b/aes.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <string>
+
+namespace AES{
+
+	enum Algorithm{
+		AES_128,
+		AES_192,
+		AES_256,
+	};
+
+	std::string encrypt(const std::string &key,const std::string &data,Algorithm algo);
+	std::string decrypt(const std::string &key,const std::string &data,Algorithm algo);
+
+}