/**
* Construct a SP800-90A Hash DRBG.
* <p>
* Minimum entropy requirement is the security strength requested.
* </p>
* @param digest source digest to use for DRB stream.
* @param securityStrength security strength required (in bits)
* @param entropySource source of entropy to use for seeding/reseeding.
* @param personalizationString personalization string to distinguish this DRBG (may be null).
* @param nonce nonce to further distinguish this DRBG (may be null).
*/
public HashSP800Drbg(IDigest digest, int securityStrength, IEntropySource entropySource, byte[] personalizationString, byte[] nonce)
{
if (securityStrength > DrbgUtilities.GetMaxSecurityStrength(digest))
{
throw new ArgumentException("Requested security strength is not supported by the derivation function");
}
if (entropySource.EntropySize < securityStrength)
{
throw new ArgumentException("Not enough entropy for security strength required");
}
mDigest = digest;
mEntropySource = entropySource;
mSecurityStrength = securityStrength;
mSeedLength = (int)seedlens[digest.AlgorithmName];
// 1. seed_material = entropy_input || nonce || personalization_string.
// 2. seed = Hash_df (seed_material, seedlen).
// 3. V = seed.
// 4. C = Hash_df ((0x00 || V), seedlen). Comment: Preceed V with a byte
// of zeros.
// 5. reseed_counter = 1.
// 6. Return V, C, and reseed_counter as the initial_working_state
byte[] entropy = GetEntropy();
byte[] seedMaterial = Arrays.ConcatenateAll(entropy, nonce, personalizationString);
byte[] seed = DrbgUtilities.HashDF(mDigest, seedMaterial, mSeedLength);
mV = seed;
byte[] subV = new byte[mV.Length + 1];
Array.Copy(mV, 0, subV, 1, mV.Length);
mC = DrbgUtilities.HashDF(mDigest, subV, mSeedLength);
mReseedCounter = 1;
}
/**
* Reseed the DRBG.
*
* @param additionalInput additional input to be added to the DRBG in this step.
*/
public void Reseed(byte[] additionalInput)
{
// 1. seed_material = 0x01 || V || entropy_input || additional_input.
//
// 2. seed = Hash_df (seed_material, seedlen).
//
// 3. V = seed.
//
// 4. C = Hash_df ((0x00 || V), seedlen).
//
// 5. reseed_counter = 1.
//
// 6. Return V, C, and reseed_counter for the new_working_state.
//
// Comment: Precede with a byte of all zeros.
byte[] entropy = GetEntropy();
byte[] seedMaterial = Arrays.ConcatenateAll(ONE, mV, entropy, additionalInput);
byte[] seed = DrbgUtilities.HashDF(mDigest, seedMaterial, mSeedLength);
mV = seed;
byte[] subV = new byte[mV.Length + 1];
subV[0] = 0x00;
Array.Copy(mV, 0, subV, 1, mV.Length);
mC = DrbgUtilities.HashDF(mDigest, subV, mSeedLength);
mReseedCounter = 1;
}