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RFC 4757, "The RC4-HMAC Kerberos Encryption Types Used by Microsoft Windows", December 2006

Source of RFC: IETF - NON WORKING GROUP
Area Assignment: sec
See Also: RFC 4757 w/ inline errata

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Errata ID: 1674
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Ganga Mahesh Siddem
Date Reported: 2009-01-30
Verifier Name: Sean Turner
Date Verified: 2011-06-28

Section 7.3 says:

                   if (encrypt)
                           RC4(Kcrypt, Token.Confounder);

                   // Sum the data buffer

                   Sgn_Cksum += MD5(data);         // Append to checksum

                   // Encrypt the data (if encrypting)

                   if (encrypt)
                           RC4(Kcrypt, data);

It should say:

                   // Sum the data buffer

                   Sgn_Cksum += MD5(data);         // Append to checksum

                   // Encrypt the  Confounder + data (if encrypting)

                   tmp=concat(Token.Confounder,data);

                   if (encrypt)
                           RC4(Kcrypt, tmp); /* tmp=Confounder + data */
               
                   memcpy(Token.Confounder,tmp,8);

                   memcpy(data,tmp+8,(tmp.len-8));             

Notes:

Notes : 1.Verified RC4 Encryption and Decryption on (Token.Confounder+Data) with Kcrypt key .
2.Verified RC4(K,x+y) !=RC4(K,x);RC4(K,y)
3.Reporting this issue after Larry's Feedback.

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