![]() With the help of the SHA-1 hash function, the password is stretched into a 128-bit key 50,000 times before opening the document as a result, the time required to crack it is vastly increased, similar to PBKDF2, scrypt or other KDFs.Įxcel and Word 2010 employed AES and a 128-bit key, but the number of SHA-1 conversions doubled to 100,000. At present there is no software that can break this encryption. In Office 2007 (Word, Excel and PowerPoint), protection was significantly enhanced since a modern protection algorithm named Advanced Encryption Standard was used. Weak passwords can still be recovered quickly even if a custom CSP is on. Choosing a non-standard Cryptographic Service Provider allows increasing the key length. In Office XP and 2003 an opportunity to use a custom protection algorithm was added. The protection presents no difficulties to hacking software. The Office-algorithm contains multiple vulnerabilities rendering it insecure. Office 97, 2000, XP and 2003 use RC4 with 40 bits. ![]() They can be cracked instantly with the help of precomputation tables. Because it's only like a Vigenere Cipher. Hacking software is now readily available to find a 16-byte key and decrypt the password-protected document. ![]() In Excel and Word 95 and prior editions a weak protection algorithm is used that converts a password to a 16-bit verifier and a 16-byte XOR obfuscation array key. History of Office Encryption Weak encryptions
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