关联数据的认证加密Aead(authenticated encryption with associated data)，是一种同时具备保密性，完整性和可认证性的加密形式，加密过程采用数据分组形式，对同一个密钥，每次加密需要使用不重复的Nonce（Number used only Once），加密后生成验证数据标签(Tag)用于解密时验证，并且可以附加一段明文数据（associated data）作为额外验证数据。
Aead加密模式的这些特征，非常适合用于随机读写文件的加密，待加密文件数据按固定大小分组，分组序号+随机初始化向量IV作为每个分组加密的Nonce，分组序号作为附加验证数据（associated data），加密文件中只需要保存块大小(BlockSize), 随机初始化向量(IV)，加密数据块(Block Cipher)即可。
在块大小和初始化向量已知的情况下，任何文件位置的数据分组序号都能被计算出来，而每次加密最小单元是一个数据块，所以可以定位文件的任何位置进行读写，即文件的随机读写。
使用流读写方法实现AeadStream，写入数据：
public override void Write(byte[] src, int offset, int count)
{
actionPos = streamPos;
var actionLen = streamLen;
initBuff(count);
int writeLen;
while (count > 0)
{
writeLen = count.min(blockSize - blockOff);
if (blockOff == 0
&& (writeLen == blockSize // overwrite whole block
|| writeLen >= actionLen - actionPos)) // overwrite exist block
{
encryptPack(src, offset, writeLen);
}
else
{
var dataLen = readFile(pack, pack.Length, blockIdx) - tagSize;
if (dataLen != (actionLen - blockIdx * blockSize).min(blockSize))
throw new Error(this, "DataError",
dataLen,
actionLen - blockIdx * blockSize);
packEnc.decrypt(pack, 0, dataLen + tagSize, blockIdx, block);
Buffer.BlockCopy(src, offset, block, blockOff, writeLen);
encryptPack(block, 0, dataLen.max(blockOff + writeLen));
}
offset += writeLen;
count -= writeLen;
actionPos += writeLen;
actionLen = actionLen.max(actionPos);
}
writeBuff();
streamPos = actionPos;
streamLen = actionLen;
}
读取数据：
public override int Read(byte[] dst, int offset, int count)
{
actionPos = streamPos;
readBuff(count);
int remain = count, dataLen, readLen;
while (remain > 0)
{
if (actionPos >= streamLen)
break;
dataLen = seekPack() - tagSize;
readLen = remain.min(dataLen - blockOff);
if (readLen <= 0)
throw new Error(this, "DataShort", remain, dataLen, blockOff);
if (blockOff == 0 && dataLen <= remain)
decryptPack(dataLen, dst, offset);
else
{
decryptPack(dataLen, block);
Buffer.BlockCopy(block, blockOff, dst, offset, readLen);
}
offset += readLen;
remain -= readLen;
actionPos += readLen;
}
streamPos = actionPos;
return count - remain;
}
定位文件位置：
long streamPos = 0;
public override long Position
{
get => streamPos;
set
{
if (value < 0 || value > Length)
throw new IOException("pos out of range!");
streamPos = value;
}
}
public override long Seek(long offset, SeekOrigin origin)
{
var pos = streamPos;
switch (origin)
{
case SeekOrigin.Begin:
pos = offset;
break;
case SeekOrigin.Current:
pos += offset;
break;
case SeekOrigin.End:
pos = streamLen - offset;
break;
}
return Position = pos;
}
AeadStream使用方法跟FileStream类似，都是Stream的标准读写方法。
完整代码：AeadStream.cs
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using util.crypt;
using util.ext;
namespace util.rep.aead
{
public class AeadStream : Stream
{
public const string Type = "aead";
public const short Version = 1;
public static byte[] KeyDomain = "file-key".utf8();
public Stream fs;
public AeadConf conf;
public static long dataSize(long fileSize, AeadConf conf)
{
var packTotal = fileSize - headSize(conf);
return (packTotal / conf.packSize()) * conf.BlockSize
+ ((packTotal % conf.packSize()) - conf.tagSize()).max(0);
}
public static int headSize(AeadConf conf)
=> Type.Length + 2 + conf.FileIdSize + conf.nonceSize();
byte[] fileId;
byte[] nonce;
public AeadStream create()
{
fileId = conf.FileIdSize.aesRnd();
nonce = aeadEnc.NonceSize.aesRnd();
var header = Type.utf8().merge(Version.bytes(), fileId, nonce);
fs.write(header);
return this;
}
public AeadStream open()
{
var header = new byte[prefix];
if (fs.readFull(header) != header.Length
|| header.utf8(0, Type.Length) != Type)
throw new Error(this, "InvalidType");
var ver = header.i16(Type.Length);
if (ver > Version)
throw new Error(this, "InvalidVersion", ver);
fileId = header.sub(Type.Length + 2, conf.FileIdSize);
nonce = header.tail(aeadEnc.NonceSize);
streamLen = dataSize(fs.Length, conf);
return this;
}
int? pre;
int prefix => (int)(pre ?? (pre = headSize(conf)));
int packSize => blockSize + tagSize;
int blockSize => conf.BlockSize;
int tagSize => aeadEnc.TagSize;
AeadCrypt ae;
AeadCrypt aeadEnc => ae ?? (ae = conf.newCrypt());
PackCrypt pke;
PackCrypt packEnc => pke ?? (pke = new PackCrypt(aeadEnc.setKey(conf.deriveKey(KeyDomain.merge(fileId), aeadEnc.KeySize)), nonce));
long actionPos;
byte[] pk;
byte[] pack => pk ?? (pk = new byte[packSize]);
byte[] blk;
byte[] block => blk ?? (blk = new byte[blockSize]);
long blockIdx => actionPos / blockSize;
int blockOff => (int)(actionPos % blockSize);
byte[] buff;
int buffLen;
int buffPos;
long buffIdx;
void initBuff(int dataLen)
{
buffLen = ((blockOff + dataLen - 1) / blockSize + 1) * packSize;
if (buff == null || buff.Length < buffLen)
buff = new byte[buffLen];
buffPos = 0;
buffIdx = blockIdx;
}
void readBuff(int dataLen)
{
initBuff(dataLen);
buffLen = readFile(buff, buffLen, buffIdx);
}
void writeBuff()
{
if (buffPos <= 0)
return;
seekFile(buffIdx);
fs.Write(buff, 0, buffPos);
}
void seekFile(long packIdx)
=> fs.Position = prefix + packIdx * packSize;
int readFile(byte[] dst, int dstLen, long packIdx)
{
seekFile(packIdx);
return fs.readFull(dst, 0, dstLen);
}
int seekPack()
{
buffPos = (int)((blockIdx - buffIdx) * packSize);
return packSize.min(buffLen - buffPos);
}
void decryptPack(int dataSize, byte[] dst, int dstOff = 0)
=> packEnc.decrypt(buff, buffPos, dataSize + tagSize, blockIdx, dst, dstOff);
void encryptPack(byte[] src, int srcOff, int srcLen)
{
packEnc.encrypt(src, srcOff, srcLen, blockIdx, buff, buffPos);
buffPos += srcLen + tagSize;
}
public override int Read(byte[] dst, int offset, int count)
{
actionPos = streamPos;
readBuff(count);
int remain = count, dataLen, readLen;
while (remain > 0)
{
if (actionPos >= streamLen)
break;
dataLen = seekPack() - tagSize;
readLen = remain.min(dataLen - blockOff);
if (readLen <= 0)
throw new Error(this, "DataShort", remain, dataLen, blockOff);
if (blockOff == 0 && dataLen <= remain)
decryptPack(dataLen, dst, offset);
else
{
decryptPack(dataLen, block);
Buffer.BlockCopy(block, blockOff, dst, offset, readLen);
}
offset += readLen;
remain -= readLen;
actionPos += readLen;
}
streamPos = actionPos;
return count - remain;
}
public override void Write(byte[] src, int offset, int count)
{
actionPos = streamPos;
var actionLen = streamLen;
initBuff(count);
int writeLen;
while (count > 0)
{
writeLen = count.min(blockSize - blockOff);
if (blockOff == 0
&& (writeLen == blockSize // overwrite whole block
|| writeLen >= actionLen - actionPos)) // overwrite exist block
{
encryptPack(src, offset, writeLen);
}
else
{
var dataLen = readFile(pack, pack.Length, blockIdx) - tagSize;
if (dataLen != (actionLen - blockIdx * blockSize).min(blockSize))
throw new Error(this, "DataError",
dataLen,
actionLen - blockIdx * blockSize);
packEnc.decrypt(pack, 0, dataLen + tagSize, blockIdx, block);
Buffer.BlockCopy(src, offset, block, blockOff, writeLen);
encryptPack(block, 0, dataLen.max(blockOff + writeLen));
}
offset += writeLen;
count -= writeLen;
actionPos += writeLen;
actionLen = actionLen.max(actionPos);
}
writeBuff();
streamPos = actionPos;
streamLen = actionLen;
}
public override long Seek(long offset, SeekOrigin origin)
{
var pos = streamPos;
switch (origin)
{
case SeekOrigin.Begin:
pos = offset;
break;
case SeekOrigin.Current:
pos += offset;
break;
case SeekOrigin.End:
pos = streamLen - offset;
break;
}
return Position = pos;
}
public override void SetLength(long value)
{
throw new NotSupportedException();
}
public override bool CanRead => fs.CanRead;
public override bool CanSeek => fs.CanSeek;
public override bool CanWrite => fs.CanWrite;
long streamLen = 0;
public override long Length => streamLen;
long streamPos = 0;
public override long Position
{
get => streamPos;
set
{
if (value < 0 || value > Length)
throw new IOException("pos out of range!");
streamPos = value;
}
}
public override void Flush() => fs.Flush();
public override void Close()
{
fs?.Close();
fs = null;
}
}
}
View Code
Github链接：
https://github.com/bsmith-zhao/vfs/blob/main/util/rep/aead/AeadStream.cs
其他参考：
https://github.com/bsmith-zhao/vfs/blob/main/util/rep/aead/AeadConf.cs
https://github.com/bsmith-zhao/vfs/tree/main/util/crypt
https://github.com/bsmith-zhao/vfs/tree/main/util/crypt/sodium
标签：加密,int,读写,writeLen,dataLen,conf,Aead,byte,public From： https://www.cnblogs.com/bsmith/p/17766307.html