iaik.cms
Class KeyTransRecipientInfo

java.lang.Object
  iaik.cms.RecipientInfo
      iaik.cms.KeyTransRecipientInfo

All Implemented Interfaces:

ASN1Type

public class KeyTransRecipientInfo
extends RecipientInfo

This class implements the CMS KeyTransRecipientInfo type.

The Cryptographic Message Syntax (CMS) (RFC 5652) specifies the KeyTransRecipientInfo type as RecipientInfo choice for collecting all recipient-related information about some particular recipient a CMS EnvelopedData or CMS AuthenticatedData object shall be sent to when the recipient has a public key to be used for encrypting the secret content-encryption key:

 KeyTransRecipientInfo ::= SEQUENCE {
    version                   CMSVersion, -- always set to 0 or 2
    rid                       RecipientIdentifier,
    keyEncryptionAlgorithm    KeyEncryptionAlgorithmIdentifier,
    encryptedKey              EncryptedKey }
 

 EncryptedKey ::= OCTET STRING
 

 RecipientIdentifier ::= CHOICE {
    issuerAndSerialNumber IssuerAndSerialNumber,
    subjectKeyIdentifier [0] SubjectKeyIdentifier }
 

The recipientIdentifier field specifies the recipient certificate (and thereby public key) by issuer distinguished name and issuer-specific serial number or SubjectKeyIdentifier. The keyEncryptionAlgorithm identifies the public-key algorithm used for encrypting the randomly generated content-encryption key with a recipient-specific public key. The encrypted content-encryption key (used for encrypting the content) is stored in the encryptedKey field.

This class provides several constructors and methods for creating a KeyTransRecipientInfo object, obtaining the component values, and encrypting (respectively decrypting) the content-encryption key.

When creating a new KeyTransRecipientInfo you immediately may supply the IssuerAndSerialNumber or SubjectKeyIdentifier or you may supply the certificate of the recipient to let this class create a certifcate identifier for it, e.g:

 // the cert of the recipient:
 X509Certificate recipientCert = ...;
 // use RSA for content key encryption:
 AlgorithmID kea = (AlgorithmID)AlgorithmID.rsaEncryption.clone();
 // create a v0 KeyTransRecipientInfo using an IssuerAndSerialNumber to point to the recipient cert:
 KeyTransRecipientInfo recipient = new KeyTransRecipientInfo(recipientCert, kea);
 

If you want to use a SubjectKeyIdentifier for pointing to the certificate of the recipient, you have to specify the CertificateIdentifier type when creating the KeyTransRecipientInfo:

 KeyTransRecipientInfo recipient = new KeyTransRecipientInfo(recipientCert, 
    CertificateIdentifier.SUBJECT_KEY_IDENTIFIER, kea);
 

The following example shows the typical usage for including a KEKRecipientInfo into a EnvelopedData object, encoding it, decoding it at the recipient side and decrypt the content (we use the stream-based EnvelopedData implementation for this sample):

 // the cert of the recipient:
 X509Certificate recipientCert = ...;
 // use RSA for content key encryption:
 AlgorithmID kea = (AlgorithmID)AlgorithmID.rsaEncryption.clone();
 // create a v0 KeyTransRecipientInfo using an IssuerAndSerialNumber to point to the recipient cert:
 KeyTransRecipientInfo recipient = new KeyTransRecipientInfo(recipientCert, kea);
 // create an EnvelopedData for the content to be encrypted:
 EnvelopedDataStream envelopedData = new EnvelopedDataStream(is, (AlgorithmID)AlgorithmID.aes256_CBC.clone());
 // add the recipient information:
 envelopedData.addRecipientInfo(recipient);
 // write the EnvelopedData to a stream thereby performing the content encryption:
 int blockSize = ...;
 OutputStream encoded_stream = ...;
 envelopedData.writeTo(encoded_stream, blockSize);
 ...
 // on the recipient side decode the EnvelopedData:
 InputStream encodedStream = ...;
 EnvelopedDataStream envelopedData = new EnvelopedData(encodedStream);
 // Get information about the inherent EncryptedContentInfo:
 EncryptedContentInfoStream eci = (EncryptedContentInfoStream)enveloped_data.getEncryptedContentInfo();
 System.out.println("Content type: "+eci.getContentType().getName());
 System.out.println("Content encryption algorithm: "+eci.getContentEncryptionAlgorithm().getName());
 // setup the cipher for decryption:
 envelopedData.setupCipher(recipientPrivateKey, recipientCert);
 // read the content thereby performing the content decryption:
 InputStream data_is = enveloped_data.getInputStream();
 byte[] buf = new byte[2048];
 int r;
 while ((r = data_is.read(buf)) > 0) {
   // do something useful
 }
 

See Also:

IssuerAndSerialNumber, SubjectKeyID, RecipientInfo

Field Summary

Fields inherited from class iaik.cms.RecipientInfo

KEK_RECIPIENT_INFO, KEY_AGREE_RECIPIENT_INFO, KEY_TRANSPORT_RECIPIENT_INFO, keyEncryptionAlgorithm_, OTHER_RECIPIENT_INFO, PASSWORD_RECIPIENT_INFO, securityProvider_, version_

Constructor Summary

KeyTransRecipientInfo()
Default Constructor.

KeyTransRecipientInfo(ASN1Object obj)
Creates a KeyTransRecipientInfo from an ASN1Object.

KeyTransRecipientInfo(CertificateIdentifier recipientIdentifier, AlgorithmID keyEA, byte[] encryptedKey)
Creates a KeyTransRecipientInfo object for the given recipient certificate identifier, key-encryption algorithm, and already encrypted content encryption key.

KeyTransRecipientInfo(CertificateIdentifier recipientIdentifier, AlgorithmID keyEA, java.security.PublicKey recipientKey)
Creates a KeyTransRecipientInfo object for the given recipient certificate identifier, key-encryption algorithm and public key of the recipient.

KeyTransRecipientInfo(X509Certificate recipientCertificate, AlgorithmID keyEA)
Creates a version 0 KeyTransRecipientInfo object from the given recipient certificate.

KeyTransRecipientInfo(X509Certificate recipientCertificate, int ridType, AlgorithmID keyEA)
Creates a KeyTransRecipientInfo object from the given recipient certificate.

Method Summary

void	decode(ASN1Object obj) Decodes the given ASN.1 KeyTransRecipientInfo object for parsing the internal structure.
javax.crypto.SecretKey	decryptKey(java.security.Key privateKey, KeyIdentifier recipientIdentifier, java.lang.String cekAlgName) Uses the given private key to decrypt the encrypted content-encryption key.
void	encryptKey(javax.crypto.SecretKey cek) Encrypts the given secret content-encryption key.
byte[]	getEncryptedKey() Returns the encrypted content-encryption key.
byte[]	getEncryptedKey(KeyIdentifier recipientIdentifier) Returns the encrypted content-encryption key for the recipient with the given keyIdentfier.
KeyIdentifier[]	getRecipientIdentifiers() Gets the key identifier belonging to the recipient of this KeyTransRecipientInfo.
java.security.PublicKey	getRecipientKey() Gets the public key of the recipient.
boolean	isRecipientInfoFor(KeyIdentifier recipientIdentifier) Checks if this is a RecipientInfo for the recipient identified by the given key identifier.
CertificateIdentifier	isRecipientInfoFor(X509Certificate recipientCertificate) Checks if this is a RecipientInfo for the given recipient certificate.
void	setEncryptedKey(byte[] encryptedKey) Sets the encrypted content-encryption key.
ASN1Object	toASN1Object() Returns this KeyTransRecipientInfo as ASN1Object.
java.lang.String	toString() Returns a string giving some information about this KeyTransRecipientInfo object.

Methods inherited from class iaik.cms.RecipientInfo

createRecipientInfos, decryptKey, decryptKey, decryptKey, getKeyEncryptionAlgorithm, getRecipientInfoType, getSecurityProvider, getVersion, parseRecipientInfo, parseRecipientInfo, parseRecipientInfo, parseRecipientInfo, parseRecipientInfos, parseRecipientInfos, setSecurityProvider

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

KeyTransRecipientInfo

public KeyTransRecipientInfo()

Default Constructor. Creates an empty KeyTransRecipientInfo object and sets the version number to 0.
Only used for dynamic object creation. Shall not be used by an application.

KeyTransRecipientInfo

public KeyTransRecipientInfo(CertificateIdentifier recipientIdentifier,
                             AlgorithmID keyEA,
                             byte[] encryptedKey)

Creates a KeyTransRecipientInfo object for the given recipient certificate identifier, key-encryption algorithm, and already encrypted content encryption key. The already encrypted secret key is supplied in a byte array and has been encrypted using the given key-encryption algorithm.

Parameters:

recipientIdentifier - the CertificateIdentifier identifying the recipient certificate (by IssuerAndSerialNumber or SubjectKeyIdentifier

keyEA - the ID of the key-encryption algorithm that has been used for encrypting the content-encryption key

encryptedKey - the already encrypted secret key

KeyTransRecipientInfo

public KeyTransRecipientInfo(CertificateIdentifier recipientIdentifier,
                             AlgorithmID keyEA,
                             java.security.PublicKey recipientKey)

Creates a KeyTransRecipientInfo object for the given recipient certificate identifier, key-encryption algorithm and public key of the recipient.

Parameters:

recipientIdentifier - the CertificateIdentifier identifying the recipient certificate (by IssuerAndSerialNumber or SubjectKeyIdentifier

keyEA - the ID of the key-encryption algorithm to be used for encrypting the content-encryption key

recipientKey - the public key of the recipient to be used for encrypting the content-encryption key

Throws:

java.lang.IllegalArgumentException - if the supplied recipientIdentifier is not a SubjectKeyID or IssuerAndSerialNumber

KeyTransRecipientInfo

public KeyTransRecipientInfo(X509Certificate recipientCertificate,
                             AlgorithmID keyEA)

Creates a version 0 KeyTransRecipientInfo object from the given recipient certificate.

From the given certificate an IssuerAndSerialNumber is created to be used as recipient identifier for pointing to the certificate of the recipient. The public key from the given certificate will be used to encrypt the symmetric content-encryption key with the given key-encryption algorithm when calling the encryptKey method.

Parameters:

recipientCertificate - the certificate of the recipient

keyEA - the algorithm for encrypting the symmetric content-encryption key

KeyTransRecipientInfo

public KeyTransRecipientInfo(X509Certificate recipientCertificate,
                             int ridType,
                             AlgorithmID keyEA)
                      throws X509ExtensionException

Creates a KeyTransRecipientInfo object from the given recipient certificate.

From the given certificate an IssuerAndSerialNumber or SubjectKeyIdentifier (depending on the requested recipient identifier type) is created to be used as recipient identifier for pointing to the certificate of the recipient. The public key from the given certificate will be used to encrypt the symmetric content-encryption key with the given key-encryption algorithm when calling the encryptKey method.

Parameters:

recipientCertificate - the certificate of the recipient

ridType - the type of the recipientIdentifier, either CertificateIdentifier.ISSUER_AND_SERIALNUMBER or CertificateIdentifier.SUBJECT_KEY_IDENTIFIER

keyEA - the algorithm for encrypting the symmetric key

Throws:

X509ExtensionException - if a SubjectKeyIdentifier shall be used as recipientIdentifier, but the given cert does contain the SubjectKeyIdentifier extension or the SubjectKeyIdentifier extension cannot be parsed

java.lang.IllegalArgumentException - if the request recipientIdentifier type is not ISSUER_AND_SERIALNUMBER or SUBJECT_KEY_IDENTIFIER

KeyTransRecipientInfo

public KeyTransRecipientInfo(ASN1Object obj)
                      throws CodingException

Creates a KeyTransRecipientInfo from an ASN1Object.

The ASN1Object supplied to this constructor represents an already exisiting KeyTransRecipientInfo object that may have been created by calling toASN1Object.

Parameters:

obj - the KeyTransRecipientInfo as ASN1Object

Throws:

CodingException - if the object can not be parsed

Method Detail

decode

public void decode(ASN1Object obj)
            throws CodingException

Decodes the given ASN.1 KeyTransRecipientInfo object for parsing the internal structure.

This method internally is called when creating a CMS KeyTransRecipientInfo object from an already existing KeyTransRecipientInfo object, supplied as ASN1Object.

Parameters:

obj - the CMS KeyTransRecipientInfo as ASN1Object

Throws:

CodingException - if the object can not be parsed

toASN1Object

public ASN1Object toASN1Object()

Returns this KeyTransRecipientInfo as ASN1Object.

The ASN1Object returned by this method represents the ASN.1 structure of a KeyTransRecipientInfo:

 KeyTransRecipientInfo ::= SEQUENCE {
    version                   CMSVersion, -- always set to 0 or 2
    rid                       RecipientIdentifier,
    keyEncryptionAlgorithm    KeyEncryptionAlgorithmIdentifier,
    encryptedKey              EncryptedKey }
 

 EncryptedKey ::= OCTET STRING
 

 RecipientIdentifier ::= CHOICE {
  issuerAndSerialNumber IssuerAndSerialNumber,
 subjectKeyIdentifier [0] SubjectKeyIdentifier }
 

Returns:

this KeyTransRecipientInfo as ASN1Object.

decryptKey

public javax.crypto.SecretKey decryptKey(java.security.Key privateKey,
                                         KeyIdentifier recipientIdentifier,
                                         java.lang.String cekAlgName)
                                  throws CMSException,
                                         java.security.InvalidKeyException

Uses the given private key to decrypt the encrypted content-encryption key. The recovered key is returned as SecretKey.

This method implements the same named method of the abstract parent RecipientInfo class. Since a KeyTransRecipientInfo only represents one single recipient the supplied recipientIdentifier may be null.

Specified by:

decryptKey in class RecipientInfo

Parameters:

privateKey - the private key of the recipient to be used for decrypting the encrypted content-encryption key.

recipientIdentifier - an IssuerAndSerialNumber or SubjectKeyIdentifier identifying the recipient of this KeyTransRecipientInfo

cekAlgName - the name of the content encryption key (e.g. "AES") to be set for the SecretKey object created by this method

Returns:

the recovered (decrypted) key as SecretKey in RAW format

Throws:

CMSException - if the key-decryption process fails for some reason (e.g. the key-encryption algorithm used by this KeyTransRecipientInfo is not implemented, a padding error occurs,...)

java.security.InvalidKeyException - if the specified private key is not valid

encryptKey

public void encryptKey(javax.crypto.SecretKey cek)
                throws CMSException

Encrypts the given secret content-encryption key.

All information (key encryption algorithm, public key of the recipient) has been supplied when creating this KeyTransRecipientInfo object.

Specified by:

encryptKey in class RecipientInfo

Parameters:

cek - the symmetric content-encryption key to encrypt

Throws:

CMSException - if the key encryption process fails for some reason (e.g. the key-encryption algortihm used by this KeyTransRecipientInfo is not implemented, the public key of the recipient is Invalid, a padding error occurs,...)

getRecipientIdentifiers

public KeyIdentifier[] getRecipientIdentifiers()

Gets the key identifier belonging to the recipient of this KeyTransRecipientInfo.

This method implements the same named method of the abstract parent RecipientInfo class for returning an identifier of the recipient's certificate (and thereby public key) by issuer distinguished name and issuer-specific serial number, or SubjectKeyIdentifier. Since only one recipient is represented by a KeyTransRecipientInfo the KeyIdentifier array returned by this method only will contain one single KeyIdentifier object.

Specified by:

getRecipientIdentifiers in class RecipientInfo

Returns:

an KeyIdentifier array holding an identifier of the recipient's certificate (and thereby public key) by IssuerAndSerialNumber or SubjectKeyID

isRecipientInfoFor

public boolean isRecipientInfoFor(KeyIdentifier recipientIdentifier)

Checks if this is a RecipientInfo for the recipient identified by the given key identifier.

Specified by:

isRecipientInfoFor in class RecipientInfo

Parameters:

recipientIdentifier - the key identifier belonging to the recipient we are searching for

Returns:

true if this RecipientInfo belongs to the particular recipient in mind, false if not

isRecipientInfoFor

public CertificateIdentifier isRecipientInfoFor(X509Certificate recipientCertificate)

Checks if this is a RecipientInfo for the given recipient certificate.

Specified by:

isRecipientInfoFor in class RecipientInfo

Parameters:

recipientCertificate - the certificate of the recipient

Returns:

the CertificateIdentifier indicating that the recipient with the given certificate is the owner of this RecipientInfo, null if not

setEncryptedKey

public void setEncryptedKey(byte[] encryptedKey)

Sets the encrypted content-encryption key.

Parameters:

encryptedKey - the encrypted content-encryption key

getEncryptedKey

public byte[] getEncryptedKey()

Returns the encrypted content-encryption key. The key has been encrypted with the recipient public key.

Returns:

the encrypted content-encryption key

getRecipientKey

public java.security.PublicKey getRecipientKey()

Gets the public key of the recipient. Only meaningful at the sender side where the key of the recipient is needed for encrypting the content-encryption-key.

Returns:

the public key of the recipient or null if the recipient key is not set

getEncryptedKey

public byte[] getEncryptedKey(KeyIdentifier recipientIdentifier)
                       throws CMSException

Returns the encrypted content-encryption key for the recipient with the given keyIdentfier.

This method implements the same named method of the abstract parent RecipientInfo class for asking if this KeyTransRecipientInfo holds an encrypted key for the recipient identified by the given key identifier (IssuerAndSerialNumber or SubjectKeyIdentifier). Since a KeyTransRecipientInfo only represents one single recipient the supplied recipientIdentifier may be null.

Specified by:

getEncryptedKey in class RecipientInfo

Parameters:

recipientIdentifier - information to be used for getting the right encrypted content encryption key for the right recipient; may be not required for a KeyTransRecipientInfo, but for KeyAgreeRecipientInfo) which may hold encrypted content encryption keys for more than one recipient; may be null for only getting the encrypted content-encryption key included

Returns:

the encrypted content-encryption key for the recipient with the given key identifier

Throws:

CMSException - if this KeyTransRecipientInfo does not belong to the recipient with the given key identifier is included

toString

public java.lang.String toString()

Returns a string giving some information about this KeyTransRecipientInfo object.

Specified by:

toString in class RecipientInfo

Returns:

the string representation