ファイル暗号化で共有キーを作成する方法

ファイル暗号化で共有キーを作成する方法
VB.NET

Private Shared Sub GenerateKeyFromPassword(ByVal password As String, _
                                           ByVal keySize As Integer, _
                                           ByRef key As Byte(), _
                                           ByVal blockSize As Integer, _
                                           ByRef iv As Byte())
    Dim salt As Byte() = System.Text.Encoding.UTF8.GetBytes("saltは必ず8バイト以上")
    Dim deriveBytes As New System.Security.Cryptography.Rfc2898DeriveBytes( _
        password, salt)
    deriveBytes.IterationCount = 1000

    key = deriveBytes.GetBytes(keySize \ 8)
    iv = deriveBytes.GetBytes(blockSize \ 8)
End Sub

Public Shared Sub EncryptFile(ByVal sourceFile As String, _
                              ByVal destFile As String, _
                              ByVal password As String)
    Dim rijndael As New System.Security.Cryptography.RijndaelManaged()

    Dim key As Byte(), iv As Byte()
    GenerateKeyFromPassword(password, rijndael.KeySize, key, rijndael.BlockSize, iv)
    rijndael.Key = key
    rijndael.IV = iv

    Dim outFs As New System.IO.FileStream( _
        destFile, System.IO.FileMode.Create, System.IO.FileAccess.Write)
    Dim encryptor As System.Security.Cryptography.ICryptoTransform = _
        rijndael.CreateEncryptor()
    Dim cryptStrm As New System.Security.Cryptography.CryptoStream( _
        outFs, encryptor, System.Security.Cryptography.CryptoStreamMode.Write)

    Dim inFs As New System.IO.FileStream( _
        sourceFile, System.IO.FileMode.Open, System.IO.FileAccess.Read)
    Dim bs As Byte() = New Byte(1023) {}
    Dim readLen As Integer
    While True
        readLen = inFs.Read(bs, 0, bs.Length)
        If readLen = 0 Then
            Exit While
        End If
        cryptStrm.Write(bs, 0, readLen)
    End While

    inFs.Close()
    cryptStrm.Close()
    encryptor.Dispose()
    outFs.Close()
End Sub

Public Shared Sub DecryptFile(ByVal sourceFile As String, _
                              ByVal destFile As String, _
                              ByVal password As String)
    Dim rijndael As New System.Security.Cryptography.RijndaelManaged()

    Dim key As Byte(), iv As Byte()
    GenerateKeyFromPassword(password, rijndael.KeySize, key, rijndael.BlockSize, iv)
    rijndael.Key = key
    rijndael.IV = iv

    Dim inFs As New System.IO.FileStream( _
        sourceFile, System.IO.FileMode.Open, System.IO.FileAccess.Read)
    Dim decryptor As System.Security.Cryptography.ICryptoTransform = _
        rijndael.CreateDecryptor()
    Dim cryptStrm As New System.Security.Cryptography.CryptoStream( _
        inFs, decryptor, System.Security.Cryptography.CryptoStreamMode.Read)

    Dim outFs As New System.IO.FileStream( _
        destFile, System.IO.FileMode.Create, System.IO.FileAccess.Write)
    Dim bs As Byte() = New Byte(1023) {}
    Dim readLen As Integer
    While True
        readLen = cryptStrm.Read(bs, 0, bs.Length)
        If readLen = 0 Then
            Exit While
        End If
        outFs.Write(bs, 0, readLen)
    End While

    outFs.Close()
    cryptStrm.Close()
    decryptor.Dispose()
    inFs.Close()
End Sub

C#

private static void GenerateKeyFromPassword(string password,
    int keySize, out byte[] key, int blockSize, out byte[] iv)
{
    byte[] salt = System.Text.Encoding.UTF8.GetBytes("saltは必ず8バイト以上");
    System.Security.Cryptography.Rfc2898DeriveBytes deriveBytes =
        new System.Security.Cryptography.Rfc2898DeriveBytes(password, salt);
    deriveBytes.IterationCount = 1000;

    key = deriveBytes.GetBytes(keySize / 8);
    iv = deriveBytes.GetBytes(blockSize / 8);
}

public static void EncryptFile(
    string sourceFile, string destFile, string password)
{
    System.Security.Cryptography.RijndaelManaged rijndael =
        new System.Security.Cryptography.RijndaelManaged();

    byte[] key, iv;
    GenerateKeyFromPassword(
        password, rijndael.KeySize, out key, rijndael.BlockSize, out iv);
    rijndael.Key = key;
    rijndael.IV = iv;

    System.IO.FileStream outFs = new System.IO.FileStream(
        destFile, System.IO.FileMode.Create, System.IO.FileAccess.Write);
    System.Security.Cryptography.ICryptoTransform encryptor =
        rijndael.CreateEncryptor();
    System.Security.Cryptography.CryptoStream cryptStrm =
        new System.Security.Cryptography.CryptoStream(
            outFs, encryptor,
            System.Security.Cryptography.CryptoStreamMode.Write);

    System.IO.FileStream inFs = new System.IO.FileStream(
        sourceFile, System.IO.FileMode.Open, System.IO.FileAccess.Read);
    byte[] bs = new byte[1024];
    int readLen;
    while ((readLen = inFs.Read(bs, 0, bs.Length)) > 0)
    {
        cryptStrm.Write(bs, 0, readLen);
    }

    inFs.Close();
    cryptStrm.Close();
    encryptor.Dispose();
    outFs.Close();
}

public static void DecryptFile(
    string sourceFile, string destFile, string password)
{
    System.Security.Cryptography.RijndaelManaged rijndael =
        new System.Security.Cryptography.RijndaelManaged();

    byte[] key, iv;
    GenerateKeyFromPassword(
        password, rijndael.KeySize, out key, rijndael.BlockSize, out iv);
    rijndael.Key = key;
    rijndael.IV = iv;

    System.IO.FileStream inFs = new System.IO.FileStream(
        sourceFile, System.IO.FileMode.Open, System.IO.FileAccess.Read);
    System.Security.Cryptography.ICryptoTransform decryptor =
        rijndael.CreateDecryptor();
    System.Security.Cryptography.CryptoStream cryptStrm =
        new System.Security.Cryptography.CryptoStream(
            inFs, decryptor,
            System.Security.Cryptography.CryptoStreamMode.Read);

    System.IO.FileStream outFs = new System.IO.FileStream(
        destFile, System.IO.FileMode.Create, System.IO.FileAccess.Write);
    byte[] bs = new byte[1024];
    int readLen;
    while ((readLen = cryptStrm.Read(bs, 0, bs.Length)) > 0)
    {
        outFs.Write(bs, 0, readLen);
    }

    outFs.Close();
    cryptStrm.Close();
    decryptor.Dispose();
    inFs.Close();
}