Encrypt a Document

Encryption is the process that translates readable text to meaningless sequences of bytes so it can only be read by the person who has the decryption key or the secret code. This process plays an important role in securing your content. It helps to encode the content, verify the origin of a document, prove that the content has not been modified after it was sent, and ensure that the data from the document is safe.

This article explains how Aspose.Words allows you to encrypt a document and how to check if a document has encryption or not.

Encrypt with Password

To encrypt a document, use the Password property to provide a password that functions as an encryption key. This will modify the content of your document and make it unreadable. The encrypted document will require to have this password entered before it can be opened.

You can find the appropriate Password property for the required format. Each document save format has a corresponding class containing save options for this format. For example, the Password property in the DocSaveOptions class for DOC, or the Password property in the OoxmlSaveOptions class for DOCX, DOCM, DOTX, DOTM, and FlatOpc.

Note that only certain document formats support encryption. For example, RTF does not support encryption.

The table below lists the formats and encryption algorithms supported by Aspose.Words:

Format	Supported Encryption while Loading	Supported Encryption while Saving
DOC, DOT	XOR encryption40-bit RC4 EncryptionCryptoAPI RC4 Encryption	RC4 Encryption (40-bit)
DOCX, DOTX, DOCM, DOTM, FlatOPC, FlatOpcTemplate, FlatOpcMacroEnabled, FlatOpcTemplateMacroEnabled	ECMA-376 Standard EncryptionECMA-376 Agile Encryption	ECMA-376 Standard Encryption (AES128 + SHA1)
ODT, OTT	ODF Encryption (Blowfish/AES)	ODF Encryption (AES256 + SHA256)
PDF	-	RC4 Encryption (40/128 bit)

The following code example shows how to encrypt a document with a password:

Check If a Document Is Encrypted

In some cases, you may have an unreadable document and want to be sure that the document is encrypted and not corrupted or compressed.

To detect if a document is encrypted and if a password is required, you can use the IsEncrypted property of the FileFormatInfo class. This property will also allow you to perform some action before loading a document, for example, informing a user to provide a password.

The following code example shows how to detect the document encryption:

Open a Document With or Without a Password

When we have made sure that a document is encrypted, we can try to open this document without a password, which should lead to an exception.

The following code example shows how to try opening an encrypted document without a password:

After we have seen that an encrypted document cannot be opened without a password, we can try to open it by entering the password.

The following code example shows how to try opening an encrypted document with a password:

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FAQ

1. Q: How do I encrypt a Word document with a password using Aspose.Words for Java?
   A: Use the appropriate save‑options class for the target format (e.g., DocSaveOptions for DOC or OoxmlSaveOptions for DOCX) and set its setPassword("yourPassword") method before calling Document.save. The document will be saved encrypted and will require the password to open.

2. Q: Which file formats support encryption when saving with Aspose.Words for Java?
   A: DOC, DOCX, DOCM, DOTX, DOTM, FlatOPC, ODT, OTT, and PDF support encryption. Formats such as RTF do not support encryption. Each format uses its own set of supported algorithms (e.g., RC4 for DOC, ECMA‑376 AES128 for DOCX, AES256 for ODT, RC4 for PDF).

3. Q: How can I determine whether a document is encrypted before loading it?
   A: Create a FileFormatInfo instance by calling FileFormatUtil.detectFileFormat(filePath). Then check the isEncrypted() property. If it returns true, the document is encrypted and you must supply the password when loading.

4. Q: What exception is thrown if I try to open an encrypted document without providing a password?
   A: Aspose.Words throws a IncorrectPasswordException. Catch this exception to prompt the user for the correct password or to handle the error gracefully.

5. Q: Can I choose a different encryption algorithm for a specific format?
   A: Yes. Each save‑options class exposes algorithm‑specific properties (e.g., setEncryptionAlgorithm(EncryptionAlgorithm.AES256) for ODT or setEncryptionAlgorithm(EncryptionAlgorithm.RC4_128) for PDF). Set the desired algorithm before saving the document.