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Ms office 2010 Encrypted File (Agile Encryption) opening RRS feed

  • Question

  • hi.

    I'm working on ms office 2010 opening  encrypted file.

    I do not understand the open algorithm clearly, but I will show my procedure and questions.

    If somebody know the currect things, please explain me very specific.

     

    I want to make encryptedVerifierHashInput value.

     

    Here is my sample tags - 

    <encryption xmlns="http://schemas.microsoft.com/office/2006/encryption"xmlns:p="http://schemas.microsoft.com/office/2006/keyEncryptor/password">
    <keyData saltSize="16" blockSize="16" keyBits="128" hashSize="20" cipherAlgorithm="AES" cipherChaining="ChainingModeCBC"hashAlgorithm="SHA1" saltValue="cIJbDY9n789Oo5XBSU0lxA=="/>
    <dataIntegrity encryptedHmacKey="PqcXib+YmedKn67o0D/FeH+d/gWAucPIiRpCagUnRXs="encryptedHmacValue="kl0wXelJ5a3hztABvshT1sahO5K6AbM2muv6Wzw3EUU="/>
     <keyEncryptors>
     <keyEncryptor uri="http://schemas.microsoft.com/office/2006/keyEncryptor/password">
    <p:encryptedKey spinCount="100000" saltSize="16" blockSize="16" keyBits="128" hashSize="20" cipherAlgorithm="AES"cipherChaining="ChainingModeCBC"
      hashAlgorithm="SHA1" saltValue="lS+abMy38y58Ktf53+SBCA=="encryptedVerifierHashInput="oSRgauy9ilU9+t+nJD1xjA=="
      encryptedVerifierHashValue="xzY+E5Grj3/sZTAJZdiuE67wWbJRnUV8/TQIterZ7xs=" encryptedKeyValue="54ECzuGmskUQjPwcDyzh8A=="/>
    </keyEncryptor>
    </keyEncryptors>
    </encryption>

     

    Office Documents cryptography structure specification(2.3.4.11) says

     H0 = H(salt + Password).

    To make the salt value we use base64decoding function.

    That means

               Salt = base64decodingfunction(saltValue).

    Q1. In the sample tags, there are two saltvalues which are "cIJbDY9n789Oo5XBSU0lxA==" and "lS+abMy38y58Ktf53+SBCA==". Which one is right value to make salt?

     

    Q2.  2.3.4.11(encryptions key generation) says

    Hfinal = H(Hn + block_key).

     I'm wondering if Hfinal is same with keysalt(2.3.4.12 Initialization vector generation)?

    Hfinal = keysalt?

    Wednesday, January 25, 2012 6:04 AM

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