Encrypt and Decrypt Excel files

Microsoft Excel (97–365) enables you to encrypt/password‑protect your spreadsheets. It utilizes algorithms provided by a Crypto Service Provider. A Crypto Service Provider (CSP) is a set of cryptographic algorithms with different properties. The default CSP is “Office 97/2000 Compatible” or “Weak Encryption (XOR)". It’s also important to choose a proper encryption key length. Some Crypto Service Providers don’t support more than 40 or 56 bits; that is considered a weak encryption type. However, for strong encryption, a minimum key length of 128 bits is required. Microsoft Windows contains Crypto Service Providers that offer strong encryption types as well, for example, the Microsoft Strong Cryptographic Provider. To give an idea, 128‑bit encryption is what banks use to secure connections with their Internet banking systems. Aspose.Cells allows you to encrypt/password‑protect your Excel files with your desired encryption type.

Using MS Excel

In MS Excel (e.g., MS Excel 2003), to implement file‑encryption settings, you may try:

• From the Tools menu, select Options, and then select the Security tab.
• Input Password to open and click the Advanced button.
• Choose the encryption type and confirm the password.

Figure: Options dialog

Figure: Encryption Type dialog

Encrypting Excel file

The following example shows how you can encrypt/password‑protect an Excel file using the Aspose.Cells API.

Sample Code:

Decrypting Excel file with Aspose.Cells

It is very easy to open a password‑protected Excel file and decrypt it using the Aspose.Cells API, as shown in the following code: