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iaik.pkcs.pkcs7
Class EncryptedDataStream

java.lang.Object
  |
  +--iaik.pkcs.pkcs7.EncryptedDataStream
public class EncryptedDataStream
extends java.lang.Object
implements ContentStream

This class represents the stream-supporting implementation of the PKCS#7 EncryptedData type.

Each PKCS#7 content type is associated with a specific object identifier, derived from: 

 pkcs-7 OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) US(840) rsadsi(113549)
       pkcs(1) 7 }

The object identifier for the EncryptedData content type is defined as:

encryptedData OBJECT IDENTIFIER ::= { pkcs-7 6 }

which corresponds to the OID string "1.2.840.1.113549.1.7.6".

The PKCS#7 Cryptographic Message Standard specifies the EncryptedData content type for providing a syntax for building encrypted contents. The encrypted-data content type consists of encrypted content of any type (Version 1.5): 

 EncryptedData ::= SEQUENCE {
    version Version,
    encryptedContentInfo EncryptedContentInfo }

The encryptedContentInfo field specifies the type of the content being encrypted, the content-encryption algorithm used for encrypting the content, and the result of the content encryption. If the encrypted content value is not present in the encryptedContent field, it has to be supplied by other means: 

 EncryptedContentInfo ::= SEQUENCE {
   contentType                 ContentType,
   contentEncryptionAlgorithm  ContentEncryptionAlgorithmIdentifier,
   encryptedContent            [0] IMPLICIT EncryptedContent OPTIONAL }
 

 EncryptedContent ::= OCTET STRING

The key that is used for encrypting the content is not included in the EncryptedData structure, it is assumed to be managed by other means.

This class only can be used for creating an EncryptedData from an already encrypted content. This class supports no mechanisms for performing content encryption. When creating a new EncryptedDataStream instance the encrypted content has to be supplied as EncryptedContentInfoStream object.

Example: 

 //create a EncryptedContentInfoStream for the data to be encrypted, supplied from an input stream:
 InputStream dataStream = ...;
 EncryptedContentInfoStream eci = new EncryptedContentInfoStream(ObjectID.pkcs7_data, dataStream);
 //generate secret key and set up the cipher for encryption:
 SecretKey key = eci.setupCipher(AlgorithmID.des_EDE3_CBC);
 //create an EncryptedDataStream for the EncryptedContentInfoStream:
 EncryptedDataStream encrypted_data = new EncryptedDataStream(eci);
 //DER encode the EncryptedDataStream structure and write the encoding to an
 //output stream:
 OutputStream encoded_stream = ...;
 int blockSize = ...;
 encrypted_data.writeTo(encoded_stream, blockSize);
If a positive blocksize is specified, the encrypted content of the inherent EncryptedContentInfoStream will be encoded as indefinite primitive octet string instead of using the default primitive definite encoding scheme: 
 0x24 0x80
           0x04 <blocksize> <first encrypted content block>
           0x04 <blocksize> <second encrypted content block>
           0x04 <blocksize> <third encrypted content block>
                ...
 0x00 0x00
instead of: 
 0x04 <length> <encrypted content>
The indefinte constrcuted encoding scheme may be preferable for properly handling large amounts of data, or/and when intending to be compatible to the encoding practice of some particular application (for instance some versions of Netscape Navigator).

Decrypting goes the reverse way: From the DER encoded encryptedData a new EncryptedDataStream is created and parsed for the inherent EncryptedContentInfoStream. From the EncryptedContentInfoStream the encrypted content is obtained and decrypted using the same secret key: 

 EncryptedDataStream encryptedData = new EncryptedDataStream(encoded_stream);
 EncryptedContentInfoStream eci =  (EncryptedContentInfoStream)encryptedData.getEncryptedContentInfo();
 //setup the cipher for decryption using the right secret key:
 eci.setupCipher(key);
 //get and read the data thereby actually performing the decryption
 InputStream data_is = signed_data.getInputStream();
 byte[] buf = new byte[1024];
 int r;
 while ((r = data_is.read(buf)) > 0) {
   // do something useful 
 }

See Also:
EncryptedContentInfoStream

Field Summary
protected  int block_size
          The block size for block oriented stream encoding.
protected  int version
          This class implements version 0 of the standard
 
Constructor Summary
protected EncryptedDataStream()
          Default constructor for dynamic object creation in ContentInfo.
  EncryptedDataStream(EncryptedContentInfoStream encryptedContentInfo)
          Creates a PKCS#7 EncryptedDataStream from an EncryptedContentInfoStream.
  EncryptedDataStream(java.io.InputStream is)
          Creates a new EncryptedDataStream where the DER encoded data is read from the given InputStream.
 
Method Summary
 void decode(java.io.InputStream is)
          Reads and decodes the EncryptedDataStream from a DerInputStream.
 ObjectID getContentType()
          Returns the content type this class implements.
 java.lang.Object getEncryptedContentInfo()
          Returns the encrypted content info of this EncryptedDataStream object.
 int getVersion()
          Returns the syntax version number.
 void setBlockSize(int blockSize)
          Sets the block size for defining the length of each definite primitive encoded octet string component.
 ASN1Object toASN1Object()
          Returns this PKCS#7 EnvelopedDataStream as ASN1Object.
protected  ASN1Object toASN1Object(int blockSize)
          Returns this PKCS#7 EncryptedDataStream as ASN1Object where a constructed OCTET STRING is used for encoding the encrypted content.
 java.lang.String toString()
          Returns a string giving some information about this EncryptedDataStream object.
 java.lang.String toString(boolean detailed)
          Returns a string giving some - if requested - detailed information about this EncryptedDataStream object.
 void writeTo(java.io.OutputStream os)
          BER encodes and writes this EnvelopedDataStream to the supplied output stream.
 void writeTo(java.io.OutputStream os, int blockSize)
          Writes this object to the supplied output stream where a constructed OCTET STRING is used for encoding the content.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

version

protected int version
This class implements version 0 of the standard

block_size

protected int block_size
The block size for block oriented stream encoding.
Constructor Detail

EncryptedDataStream

protected EncryptedDataStream()
Default constructor for dynamic object creation in ContentInfo.

EncryptedDataStream

public EncryptedDataStream(EncryptedContentInfoStream encryptedContentInfo)
Creates a PKCS#7 EncryptedDataStream from an EncryptedContentInfoStream.
Parameters:
encryptedContentInfo - the already created encrypted content info

EncryptedDataStream

public EncryptedDataStream(java.io.InputStream is)
                    throws java.io.IOException,
                           PKCSParsingException
Creates a new EncryptedDataStream where the DER encoded data is read from the given InputStream.
Parameters:
is - the InputStream holding a DER encoded PKCS#7 EncryptedDataStream object
Throws:
java.io.IOException - if an I/O error occurs during reading from the InputStream
PKCSParsingException - if an error occurs while parsing the object
Method Detail

setBlockSize

public void setBlockSize(int blockSize)
Sets the block size for defining the length of each definite primitive encoded octet string component. If the value of blockSize is smaller or equal to zero the whole data is encoded as definite primitive octet string. This method may be used for enforcing block encoding when wrapping the EncryptedData into a ContentInfo.
Specified by:
setBlockSize in interface ContentStream
Parameters:
blockSize - for defining the encoding scheme and setting the octet string component length, if positive
See Also:
OCTET_STRING

decode

public void decode(java.io.InputStream is)
            throws java.io.IOException,
                   PKCSParsingException
Reads and decodes the EncryptedDataStream from a DerInputStream. If the supplied InputStream actually is not an instance of DerInputStream, internally a DerInputStream is created before parsing the data.
Specified by:
decode in interface ContentStream
Parameters:
is - the InputStream holding a DER encoded PKCS#7 EncryptedDataStream object
Throws:
java.io.IOException - if an I/O error occurs during reading from the InputStream
PKCSParsingException - if an error occurs while parsing the object

getContentType

public ObjectID getContentType()
Returns the content type this class implements.
Specified by:
getContentType in interface ContentStream
Returns:
ObjectID.pkcs7_encryptedData

getVersion

public int getVersion()
Returns the syntax version number.
Returns:
the syntax version number

toASN1Object

public ASN1Object toASN1Object()
                        throws PKCSException
Returns this PKCS#7 EnvelopedDataStream as ASN1Object.
Specified by:
toASN1Object in interface ContentStream
Returns:
this EnvelopedData as ASN1Object.
Throws:
PKCSException - if the ASN1Object could not be created

toASN1Object

protected ASN1Object toASN1Object(int blockSize)
                           throws PKCSException
Returns this PKCS#7 EncryptedDataStream as ASN1Object where a constructed OCTET STRING is used for encoding the encrypted content.
Parameters:
blockSize - the block size defining the encoding scheme - and specifying the length of each primitive encoded octet string component, if positive
Returns:
this PKCS#7 EncryptedDataStream as ASN1Object
Throws:
PKCSException - if the ASN1Object could not be created

writeTo

public void writeTo(java.io.OutputStream os)
             throws java.io.IOException
BER encodes and writes this EnvelopedDataStream to the supplied output stream.
Parameters:
os - the output stream to which this EnvelopedDataStream shall be written

writeTo

public void writeTo(java.io.OutputStream os,
                    int blockSize)
             throws java.io.IOException
Writes this object to the supplied output stream where a constructed OCTET STRING is used for encoding the content. If a positive blocksize is specified, the encrypted content of the inherent EncryptedContentInfoStream will be encoded as indefinite primitive octet string instead of using the default primitive definite encoding scheme: 
 0x24 0x80
           0x04 <blocksize> <first encrypted content block>
           0x04 <blocksize> <second encrypted content block>
           0x04 <blocksize> <third encrypted content block>
                ...
 0x00 0x00
instead of: 
 0x04 <length> <encrypted content>
The indefinte constrcuted encoding scheme may be preferable for properly handling large amounts of data, or/and when intending to be compatible to the encoding practice of some particular application (for instance some versions of Netscape Navigator).

Parameters:
os - the output stream to which this SignedData shall be written
blockSize - the block size defining the encoding scheme - and specifying the length of each primitive encoded octet string component, if positive
Throws:
java.io.IOException - if an error occurs during writing the object

getEncryptedContentInfo

public java.lang.Object getEncryptedContentInfo()
Returns the encrypted content info of this EncryptedDataStream object. When calling this method for obtaining the inherent EncryptedContentInfoStream an explicit cast to EncryptedContentInfoStream has to be made: 
 EncryptedContentInfoStream eci = (EncryptedContentInfoStream)encrypted_data.getEncryptedContentInfo();
Returns:
the EncryptedContentInfoStream

toString

public java.lang.String toString()
Returns a string giving some information about this EncryptedDataStream object.
Overrides:
toString in class java.lang.Object
Returns:
the string representation

toString

public java.lang.String toString(boolean detailed)
Returns a string giving some - if requested - detailed information about this EncryptedDataStream object.
Specified by:
toString in interface ContentStream
Parameters:
detailed - - whether or not to give detailed information
Returns:
the string representation
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