Class PDFPassword
Identifies a PDF Password, expressible either as a string or a byte sequence.
In revisions up to version 1.e Expansion 3, the mapping between a string and the bytes corresponding to the password was poorly specified, meaning that the safest manner in which to specify a password was via a byte array. With 1.7 expansion 3, a still slightly problematic mapping was given for the Standard encryption algorithms through to version 4, and a very well specified mapping for the new version 5 encryption.
So, for passwords specified in versions up to and including 4, a byte[] representation is the most accurate, but not necessarily the most convenient manner to provide passwords. For version 5, allowing passwords to be specified as Strings will be the preferred mechanism. Rather than specify two interfaces whenever a password can be provided - one for byte[] and one for String - we express the password as a class. This class can also offer a best guess at a String representation for a password for encryption versions up to and including 4.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate static class
Converts strings to byte by employing aCharsetEncoder
and a configurable mechanism to replace or ignore characters that are unrepresentable according to the encoder.private static class
Generate byte[] representations based on a Unicode code point identity encoding; characters over 255 in value are considered unrepresentableprivate static interface
Converts a string password to a byte[] representationprivate static class
Generate byte[] representations based on the PDFDocEncoding -
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final PDFPassword
The empty passwordprivate static final PDFPassword.PasswordByteGenerator[]
An array of password byte generators that attempts to enumerate the possible strategies that an encrypting application might take to convert a string to an array of bytesprivate byte[]
the password in bytes, if specified as suchprivate String
the passwird as a string, if specified as such -
Constructor Summary
ConstructorsConstructorDescriptionPDFPassword
(byte[] passwordBytes) Construct a byte-based passwordPDFPassword
(String passwordString) Construct a string-based password -
Method Summary
Modifier and TypeMethodDescriptionprivate static List
<byte[]> generatePossiblePasswordBytes
(String passwordString) Generate some possible byte representations of a string password(package private) List
<byte[]> getPasswordBytes
(boolean unicodeConversion) Get the password bytes.private boolean
isAlphaNum7BitString
(String string) static PDFPassword
nonNullPassword
(PDFPassword password) Ensure a non-null PDFPassword by substituting the empty password for a null password
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Field Details
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EMPTY_PASSWORD
The empty password -
passwordBytes
private byte[] passwordBytesthe password in bytes, if specified as such -
passwordString
the passwird as a string, if specified as such -
PASSWORD_BYTE_GENERATORS
An array of password byte generators that attempts to enumerate the possible strategies that an encrypting application might take to convert a string to an array of bytes
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Constructor Details
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PDFPassword
public PDFPassword(byte[] passwordBytes) Construct a byte-based password- Parameters:
passwordBytes
- the password bytes
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PDFPassword
Construct a string-based password- Parameters:
passwordString
- the password
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Method Details
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nonNullPassword
Ensure a non-null PDFPassword by substituting the empty password for a null password- Parameters:
password
- the password, may be null- Returns:
- a non-null password
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getPasswordBytes
Get the password bytes.- Parameters:
unicodeConversion
- whether the specific conversion from a unicode String, as present for version 5 encryption, should be used- Returns:
- a list of possible password bytes
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generatePossiblePasswordBytes
Generate some possible byte representations of a string password- Parameters:
passwordString
- the string password- Returns:
- a list of unique possible byte representations
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isAlphaNum7BitString
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