Encrypt, decrypt, protect and unprotect Excel files

Excel workbooks often store sensitive financial, business, or personal information that must be kept from unauthorized access. Aspose.Cells for Java provides a comprehensive set of protection features that mirrors the capabilities of Microsoft Excel, allowing you to secure your data at the file level, the workbook level, and the worksheet level.

Encrypt and decrypt Excel files

A password set on an Excel file prevents unauthorized users from opening or viewing the workbook content. To encrypt a workbook, assign a password string to Workbook.Settings.Password (accessed via workbook.getSettings().setPassword(...)) and then save the workbook. Aspose.Cells writes the file in encrypted form. To open an encrypted workbook for decryption, instantiate a LoadOptions object, set LoadOptions.Password (via loadOptions.setPassword(...)) to the same password that was used during encryption, and pass it to the Workbook constructor. Aspose.Cells applies the supplied password transparently so that the rest of your code can interact with the decrypted content as if the file were a regular workbook.

import com.aspose.cells.*;
Workbook workbook = new Workbook();
Worksheet sheet = workbook.getWorksheets().get(0);
Cell cell = sheet.getCells().get("A1");
cell.putValue("Confidential Data");
workbook.getSettings().setPassword("OpenPassword123");
workbook.save("encrypted.xlsx");
LoadOptions loadOptions = new LoadOptions();
loadOptions.setPassword("OpenPassword123");
Workbook decryptedWorkbook = new Workbook("encrypted.xlsx", loadOptions);
System.out.println("Decrypted cell A1 value: " + decryptedWorkbook.getWorksheets().get(0).getCells().get("A1").getStringValue());

Read-only protection (password to modify)

Excel supports two distinct password layers. The first is a password to open, which encrypts the file itself and is covered in the previous section. The second is a password to modify, which does not block users from opening the workbook; instead, Excel recommends opening the file in read-only mode unless the modify password is supplied. Configure this behavior in Aspose.Cells through Workbook.Settings.WriteProtection (accessed via workbook.getSettings().getWriteProtection()). Set its Password property (via writeProtection.setPassword(...)) to the modify password and its Author property (via writeProtection.setAuthor(...)) to identify who applied the protection. Use the WriteProtection.validatePassword(String) method to check whether a supplied modify password is correct, returning true for a match and false otherwise.

import com.aspose.cells.*;
Workbook workbook = new Workbook();
workbook.getWorksheets().get(0).getCells().get("A1").putValue("Sample Data");
workbook.getSettings().getWriteProtection().setPassword("ModifyPwd");
workbook.getSettings().getWriteProtection().setAuthor("AuthorName");
workbook.save("WriteProtectedWorkbook.xlsx");
boolean isCorrectValid = workbook.getSettings().getWriteProtection().validatePassword("ModifyPwd");
System.out.println("ValidatePassword(\"ModifyPwd\") returned: " + isCorrectValid);
boolean isWrongValid = workbook.getSettings().getWriteProtection().validatePassword("WrongPwd");
System.out.println("ValidatePassword(\"WrongPwd\") returned: " + isWrongValid);

Protect and unprotect workbook structure

Protecting the workbook structure prevents other users from viewing hidden worksheets, adding new worksheets, moving worksheets, deleting worksheets, hiding worksheets, or renaming worksheets. The protected state applies to the sheet structure rather than the cell contents inside any sheet. To apply structure protection, call workbook.protect(ProtectionType.STRUCTURE, "password"). To remove the protection, call workbook.unprotect("password") and supply the correct password. The ProtectionType.STRUCTURE enum value is used here and is distinct from other protection types such as ProtectionType.WINDOWS.

import com.aspose.cells.*;
// Create a new workbook
Workbook workbook = new Workbook();
// Add a second worksheet
workbook.getWorksheets().add();
// Write a sample value to cell A1 of the first worksheet
workbook.getWorksheets().get(0).getCells().get(0, 0).putValue("Sample Data");
// Protect the workbook structure
workbook.protect(ProtectionType.STRUCTURE, "StructPwd");
// Save the workbook as structure_protected.xlsx
String filePath = "structure_protected.xlsx";
workbook.save(filePath);
// Reload the file into a new Workbook instance
Workbook loadedWorkbook = new Workbook(filePath);
// Remove the structure protection
loadedWorkbook.unprotect("StructPwd");
// Print confirmation message
System.out.println("Structure protection has been successfully removed from the workbook.");

Protect and unprotect worksheets

Worksheet protection locks the cells of a worksheet against accidental or deliberate changes. Users cannot edit locked cells without supplying the password. This is the typical protection used to guard formulas, headers, or designated data-entry areas in shared spreadsheets. To protect a worksheet, call worksheet.protect(ProtectionType.ALL, "password"). Using ProtectionType.ALL enables every available protection option such as selecting locked cells, formatting cells, inserting rows and columns, and deleting rows and columns. To remove the protection, call worksheet.unprotect("password") with the correct password. Finer-grained control is available by combining other protection types such as CONTENTS, OBJECTS, and SCENARIOS using bitwise OR.

import com.aspose.cells.*;
Workbook workbook = new Workbook();
Worksheet sheet = workbook.getWorksheets().get(0);
sheet.getCells().get("A1").putValue("Sample Data");
sheet.protect(ProtectionType.ALL, "SheetPwd", "SheetPwd");
workbook.save("sheet_protected.xlsx");
Workbook workbookReloaded = new Workbook("sheet_protected.xlsx");
Worksheet sheetReloaded = workbookReloaded.getWorksheets().get(0);
sheetReloaded.unprotect("SheetPwd");
System.out.println("Worksheet protection removed successfully.");

Add and validate digital signatures

A digital signature assures recipients that the workbook content is authentic and has not been altered since it was signed. Aspose.Cells provides digital signature support through the com.aspose.cells.DigitalSignatures package. The typical workflow loads a .pfx certificate file through the Java security APIs (such as java.security.KeyStore and java.security.cert.X509Certificate), wraps it in an com.aspose.cells.DigitalSignatures.DigitalSignature, adds the signature to a DigitalSignatureCollection, and applies the collection to the workbook through workbook.addDigitalSignature(DigitalSignatureCollection). The DigitalSignature.getComments() property can record signing context such as signing time and purpose. Any modification made to the workbook after signing invalidates the signature, so a validation step on the receiving side can detect tampering.

import com.aspose.cells.*;
import java.io.FileInputStream;
import java.security.KeyStore;
KeyStore pfxKeyStore = KeyStore.getInstance("PKCS12");
pfxKeyStore.load(new FileInputStream("signature.pfx"), "pfx-password".toCharArray());
DigitalSignature signature = new DigitalSignature(pfxKeyStore, "pfx-password", "Signed by Aspose.Cells", new DateTime());
DigitalSignatureCollection signatures = new DigitalSignatureCollection();
signatures.add(signature);
Workbook workbook = new Workbook();
workbook.getWorksheets().get(0).getCells().get("A1").putValue("Sample Value");
workbook.addDigitalSignature(signatures);
workbook.save("signed_workbook.xlsx");
System.out.println("The workbook has been digitally signed.");
Manage Worksheets Rows and Columns