public class X0017_StrongEncryptionHeader extends PKWareExtraHeader
Certificate-based encryption:
Value Size Description ----- ---- ----------- 0x0017 2 bytes Tag for this "extra" block type TSize 2 bytes Size of data that follows Format 2 bytes Format definition for this record AlgID 2 bytes Encryption algorithm identifier Bitlen 2 bytes Bit length of encryption key (32-448 bits) Flags 2 bytes Processing flags RCount 4 bytes Number of recipients. HashAlg 2 bytes Hash algorithm identifier HSize 2 bytes Hash size SRList (var) Simple list of recipients hashed public keys Flags - This defines the processing flags.
RCount - This defines the number intended recipients whose
public keys were used for encryption. This identifies
the number of elements in the SRList.
see also: reserved1
HashAlg - This defines the hash algorithm used to calculate
the public key hash of each public key used
for encryption. This field currently supports
only the following value for SHA-1
0x8004 - SHA1
HSize - This defines the size of a hashed public key.
SRList - This is a variable length list of the hashed
public keys for each intended recipient. Each
element in this list is HSize. The total size of
SRList is determined using RCount * HSize.
Password-based Extra Field 0x0017 in central header only.
Value Size Description ----- ---- ----------- 0x0017 2 bytes Tag for this "extra" block type TSize 2 bytes Size of data that follows Format 2 bytes Format definition for this record AlgID 2 bytes Encryption algorithm identifier Bitlen 2 bytes Bit length of encryption key (32-448 bits) Flags 2 bytes Processing flags (more?)
Format - the data format identifier for this record. The only value allowed at this time is the integer value 2.
Password-based Extra Field 0x0017 preceding compressed file data.
Value Size Description
----- ---- -----------
0x0017 2 bytes Tag for this "extra" block type
IVSize 2 bytes Size of initialization vector (IV)
IVData IVSize Initialization vector for this file
Size 4 bytes Size of remaining decryption header data
Format 2 bytes Format definition for this record
AlgID 2 bytes Encryption algorithm identifier
Bitlen 2 bytes Bit length of encryption key (32-448 bits)
Flags 2 bytes Processing flags
ErdSize 2 bytes Size of Encrypted Random Data
ErdData ErdSize Encrypted Random Data
Reserved1 4 bytes Reserved certificate processing data
Reserved2 (var) Reserved for certificate processing data
VSize 2 bytes Size of password validation data
VData VSize-4 Password validation data
VCRC32 4 bytes Standard ZIP CRC32 of password validation data
IVData - The size of the IV should match the algorithm block size.
The IVData can be completely random data. If the size of
the randomly generated data does not match the block size
it should be complemented with zero's or truncated as
necessary. If IVSize is 0,then IV = CRC32 + Uncompressed
File Size (as a 64 bit little-endian, unsigned integer value).
Format - the data format identifier for this record. The only
value allowed at this time is the integer value 2.
ErdData - Encrypted random data is used to store random data that
is used to generate a file session key for encrypting
each file. SHA1 is used to calculate hash data used to
derive keys. File session keys are derived from a master
session key generated from the user-supplied password.
If the Flags field in the decryption header contains
the value 0x4000, then the ErdData field must be
decrypted using 3DES. If the value 0x4000 is not set,
then the ErdData field must be decrypted using AlgId.
Reserved1 - Reserved for certificate processing, if value is
zero, then Reserved2 data is absent. See the explanation
under the Certificate Processing Method for details on
this data structure.
Reserved2 - If present, the size of the Reserved2 data structure
is located by skipping the first 4 bytes of this field
and using the next 2 bytes as the remaining size. See
the explanation under the Certificate Processing Method
for details on this data structure.
VSize - This size value will always include the 4 bytes of the
VCRC32 data and will be greater than 4 bytes.
VData - Random data for password validation. This data is VSize
in length and VSize must be a multiple of the encryption
block size. VCRC32 is a checksum value of VData.
VData and VCRC32 are stored encrypted and start the
stream of encrypted data for a file.
Reserved1 - Certificate Decryption Header Reserved1 Data:
Value Size Description ----- ---- ----------- RCount 4 bytes Number of recipients.
RCount - This defines the number intended recipients whose public keys were used for encryption. This defines the number of elements in the REList field defined below.
Reserved2 - Certificate Decryption Header Reserved2 Data Structures:
Value Size Description
----- ---- -----------
HashAlg 2 bytes Hash algorithm identifier
HSize 2 bytes Hash size
REList (var) List of recipient data elements
HashAlg - This defines the hash algorithm used to calculate
the public key hash of each public key used
for encryption. This field currently supports
only the following value for SHA-1
0x8004 - SHA1
HSize - This defines the size of a hashed public key
defined in REHData.
REList - This is a variable length of list of recipient data.
Each element in this list consists of a Recipient
Element data structure as follows:
Recipient Element (REList) Data Structure:
Value Size Description
----- ---- -----------
RESize 2 bytes Size of REHData + REKData
REHData HSize Hash of recipients public key
REKData (var) Simple key blob
RESize - This defines the size of an individual REList
element. This value is the combined size of the
REHData field + REKData field. REHData is defined by
HSize. REKData is variable and can be calculated
for each REList element using RESize and HSize.
REHData - Hashed public key for this recipient.
REKData - Simple Key Blob. The format of this data structure
is identical to that defined in the Microsoft
CryptoAPI and generated using the CryptExportKey()
function. The version of the Simple Key Blob
supported at this time is 0x02 as defined by
Microsoft.
For more details see https://msdn.microsoft.com/en-us/library/aa920051.aspx
Flags - Processing flags needed for decryption
See the section describing the Strong Encryption Specification for details. Refer to the section in this document entitled "Incorporating PKWARE Proprietary Technology into Your Product" for more information.
PKWareExtraHeader.EncryptionAlgorithm, PKWareExtraHeader.HashAlgorithmEXTRAFIELD_HEADER_SIZE| Constructor and Description |
|---|
X0017_StrongEncryptionHeader() |
| Modifier and Type | Method and Description |
|---|---|
PKWareExtraHeader.EncryptionAlgorithm |
getEncryptionAlgorithm()
Get encryption algorithm.
|
PKWareExtraHeader.HashAlgorithm |
getHashAlgorithm()
Get hash algorithm.
|
long |
getRecordCount()
Get record count.
|
void |
parseCentralDirectoryFormat(byte[] data,
int offset,
int length)
Parse central directory format.
|
void |
parseFileFormat(byte[] data,
int offset,
int length)
Parse file header format.
|
void |
parseFromCentralDirectoryData(byte[] data,
int offset,
int length)
Populate data from this array as if it was in central directory data.
|
void |
parseFromLocalFileData(byte[] data,
int offset,
int length)
Populate data from this array as if it was in local file data.
|
getCentralDirectoryData, getCentralDirectoryLength, getHeaderId, getLocalFileDataData, getLocalFileDataLength, setCentralDirectoryData, setLocalFileDataDatapublic long getRecordCount()
public PKWareExtraHeader.HashAlgorithm getHashAlgorithm()
public PKWareExtraHeader.EncryptionAlgorithm getEncryptionAlgorithm()
public void parseCentralDirectoryFormat(byte[] data,
int offset,
int length)
data - the buffer to read data fromoffset - offset into buffer to read datalength - the length of datapublic void parseFileFormat(byte[] data,
int offset,
int length)
(Password only?)
data - the buffer to read data fromoffset - offset into buffer to read datalength - the length of datapublic void parseFromLocalFileData(byte[] data,
int offset,
int length)
ZipExtraFieldparseFromLocalFileData in interface ZipExtraFieldparseFromLocalFileData in class PKWareExtraHeaderdata - the array of bytes.offset - the source location in the data array.length - the number of bytes to use in the data array.ZipExtraField.parseFromLocalFileData(byte[], int, int)public void parseFromCentralDirectoryData(byte[] data,
int offset,
int length)
ZipExtraFieldparseFromCentralDirectoryData in interface ZipExtraFieldparseFromCentralDirectoryData in class PKWareExtraHeaderdata - the array of bytes.offset - the source location in the data array.length - the number of bytes to use in the data array.ZipExtraField.parseFromCentralDirectoryData(byte[], int, int)"Copyright © 2010 - 2020 Adobe Systems Incorporated. All Rights Reserved"