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TD0233:  FIT Technical Decision for Contents in Selected Long Message Test – Bit-oriented Mode

Publication Date
2017.08.25

Protection Profiles
CPP_FDE_AA_V2.0, CPP_FDE_EE_V2.0

Other References
FDE_AA_SD_V2.0, FDE_EE_SD_V2.0, FCS_COP.1( b )

Issue Description

The FIT has issued a technical decision for Contents in Selected Long Message Test – Bit-oriented Mode.

Resolution

FCS_COP.1(b) in the FDE_AA_SD and FDE_EE_SD shall therefore be modified as follows:

TSS

The evaluator shall check that the association of the hash function with other TSF cryptographic functions (for example, the digital signature verification function) is documented in the TSS.
 
4.1.2.2.2 Operational Guidance

The evaluator checks the operational guidance documents to determine that any system configuration necessary to enable required hash size functionality is provided.
 
4.1.2.2.3 KMD
 
There are no KMD evaluation activities for this SFR.
 
4.1.2.2.4 Test 

The TSF hashing functions can be implemented in one of two modes. The first mode is the byte-oriented mode. In this mode the TSF only hashes messages that are an integral number of bytes in length; i.e., the length (in bits) of the message to be hashed is divisible by 8. The second mode is the bit-oriented mode. In this mode the TSF hashes messages of arbitrary length. As there are different tests for each mode, an indication is given in the following sections for the bit¬oriented vs. the byte-oriented test mode.

The evaluator shall perform all of the following tests for each hash algorithm implemented by the TSF and used to satisfy the requirements of this cPP.

Short Messages Test Bit-oriented Mode
 
The evaluators devise an input set consisting of m+1 messages, where m is the block length of the hash algorithm. The length of the messages range sequentially from 0 to m bits. The message text shall be pseudorandomly generated. The evaluators compute the message digest for each of the messages and ensure that the correct result is produced when the messages are provided to the TSF.
 
Short Messages Test Byte-oriented Mode  

The evaluators devise an input set consisting of m/8+1 messages, where m is the block length of the hash algorithm. The length of the messages range sequentially from 0 to m/8 bytes, with each  message being an integral number of bytes. The message text shall be pseudorandomly generated. The evaluators compute the message digest for each of the messages and ensure that the correct result is produced when the messages are provided to the TSF.  

Selected Long Messages Test Bit-oriented Mode  

The evaluators devise an input set consisting of m messages, where m is the block length of the hash algorithm. For SHA-256, the length of the i-th message is 512 + 99*i, where 1 ≤ i ≤ m. For SHA-512, the length of the i-th message is 1024 + 99*i, where 1 ≤ i ≤ m. The message text shall be pseudorandomly generated. The evaluators compute the message digest for each of the messages and ensure that the correct result is produced when the messages are provided to the TSF.  

Selected Long Messages Test Byte-oriented Mode  

The evaluators devise an input set consisting of m/8 messages, where m is the block length of the hash algorithm. For SHA-256, the length of the i-th message is 512 + 8*99*i, where 1 ≤ i ≤ m/8. For SHA-512, the length of the i-th message is 1024 + 8*99*i, where 1 ≤ i ≤ m/8. The message text shall be pseudorandomly generated. The evaluators compute the message digest for each of the messages and ensure that the correct result is produced when the messages are provided to the TSF. 
 
Pseudorandomly Generated Messages Test

This test is for byte-oriented implementations only. The evaluators randomly generate a seed that is n bits long, where n is the length of the message digest produced by the hash function to be tested. The evaluators then formulate a set of 100 messages and associated digests by following the algorithm provided in Figure 1 of [SHAVS]. The evaluators then ensure that the correct result is produced when the messages are provided to the TSF.

For further information, please see the FIT interpretation at: https://www.niap-ccevs.org/Documents_and_Guidance/ccevs/FITDecision201705.pdf

 

Justification

See issue description.

 
 
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