public AdditionalAuthenticatedDataTemplate(IEnumerable <string> purposes)
{
const int MEMORYSTREAM_DEFAULT_CAPACITY = 0x100; // matches MemoryStream.EnsureCapacity
var ms = new MemoryStream(MEMORYSTREAM_DEFAULT_CAPACITY);
// additionalAuthenticatedData := { magicHeader (32-bit) || keyId || purposeCount (32-bit) || (purpose)* }
// purpose := { utf8ByteCount (7-bit encoded) || utf8Text }
using (var writer = new PurposeBinaryWriter(ms))
{
writer.WriteBigEndian(MAGIC_HEADER_V0);
Debug.Assert(ms.Position == sizeof(uint));
long posPurposeCount = writer.Seek(sizeof(Guid), SeekOrigin.Current); // skip over where the key id will be stored; we'll fill it in later
writer.Seek(sizeof(uint), SeekOrigin.Current); // skip over where the purposeCount will be stored; we'll fill it in later
uint purposeCount = 0;
foreach (string purpose in purposes)
{
Debug.Assert(purpose != null);
writer.Write(purpose); // prepends length as a 7-bit encoded integer
purposeCount++;
}
// Once we have written all the purposes, go back and fill in 'purposeCount'
writer.Seek(checked ((int)posPurposeCount), SeekOrigin.Begin);
writer.WriteBigEndian(purposeCount);
}
_aadTemplate = ms.ToArray();
}
private static byte[] GenerateAdditionalAuthenticatedDataTemplateFromPurposes(string[] purposes)
{
const int MEMORYSTREAM_DEFAULT_CAPACITY = 0x100; // matches MemoryStream.EnsureCapacity
var ms = new MemoryStream(MEMORYSTREAM_DEFAULT_CAPACITY);
// additionalAuthenticatedData := { magicHeader || encryptor-GUID || purposeCount || (purpose)* }
// purpose := { utf8ByteCount || utf8Text }
using (var writer = new PurposeBinaryWriter(ms))
{
writer.WriteBigEndian(MAGIC_HEADER_V0);
Debug.Assert(ms.Position == sizeof(uint));
writer.Seek(sizeof(Guid), SeekOrigin.Current); // skip over where the encryptor GUID will be stored; we'll fill it in later
if (purposes != null)
{
writer.Write7BitEncodedInt(purposes.Length);
foreach (var purpose in purposes)
{
if (String.IsNullOrEmpty(purpose))
{
writer.Write7BitEncodedInt(0); // blank purpose
}
else
{
writer.Write(purpose);
}
}
}
else
{
writer.Write7BitEncodedInt(0); // empty purposes array
}
}
return(ms.ToArray());
}
public AdditionalAuthenticatedDataTemplate(IEnumerable<string> purposes)
{
const int MEMORYSTREAM_DEFAULT_CAPACITY = 0x100; // matches MemoryStream.EnsureCapacity
var ms = new MemoryStream(MEMORYSTREAM_DEFAULT_CAPACITY);
// additionalAuthenticatedData := { magicHeader (32-bit) || keyId || purposeCount (32-bit) || (purpose)* }
// purpose := { utf8ByteCount (7-bit encoded) || utf8Text }
using (var writer = new PurposeBinaryWriter(ms))
{
writer.WriteBigEndian(MAGIC_HEADER_V0);
Debug.Assert(ms.Position == sizeof(uint));
long posPurposeCount = writer.Seek(sizeof(Guid), SeekOrigin.Current); // skip over where the key id will be stored; we'll fill it in later
writer.Seek(sizeof(uint), SeekOrigin.Current); // skip over where the purposeCount will be stored; we'll fill it in later
uint purposeCount = 0;
foreach (string purpose in purposes)
{
Debug.Assert(purpose != null);
writer.Write(purpose); // prepends length as a 7-bit encoded integer
purposeCount++;
}
// Once we have written all the purposes, go back and fill in 'purposeCount'
writer.Seek(checked((int)posPurposeCount), SeekOrigin.Begin);
writer.WriteBigEndian(purposeCount);
}
_aadTemplate = ms.ToArray();
}
