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sapphire.cpp

// sapphire.cpp -- modified by Wei Dai from:

/* sapphire.cpp -- the Saphire II stream cipher class.
   Dedicated to the Public Domain the author and inventor:
   (Michael Paul Johnson).  This code comes with no warranty.
   Use it at your own risk.
   Ported from the Pascal implementation of the Sapphire Stream
   Cipher 9 December 1994.
   Added hash pre- and post-processing 27 December 1994.
   Modified initialization to make index variables key dependent,
   made the output function more resistant to cryptanalysis,
   and renamed to Sapphire II 2 January 1995
*/

#include "pch.h"
#include "sapphire.h"

NAMESPACE_BEGIN(CryptoPP)

byte SapphireBase::keyrand(unsigned int limit,
                                                   const byte *user_key,
                                                   byte keysize,
                                                   byte *rsum,
                                                   unsigned *keypos)
{
        unsigned u,             // Value from 0 to limit to return.
                retry_limiter,      // No infinite loops allowed.
                mask;               // Select just enough bits.

        retry_limiter = 0;
        mask = 1;               // Fill mask with enough bits to cover
        while (mask < limit)    // the desired range.
                mask = (mask << 1) + 1;
        do
                {
                *rsum = cards[*rsum] + user_key[(*keypos)++];
                if (*keypos >= keysize)
                        {
                        *keypos = 0;            // Recycle the user key.
                        *rsum += keysize;   // key "aaaa" != key "aaaaaaaa"
                        }
                u = mask & *rsum;
                if (++retry_limiter > 11)
                        u %= limit;     // Prevent very rare long loops.
                }
        while (u > limit);
        return u;
}

SapphireBase::SapphireBase()
        : cards(256)
{
}

SapphireBase::SapphireBase(const byte *key, unsigned int keysize)
        : cards(256)
{
        assert(keysize < 256);
        // Key size may be up to 256 bytes.
        // Pass phrases may be used directly, with longer length
        // compensating for the low entropy expected in such keys.
        // Alternatively, shorter keys hashed from a pass phrase or
        // generated randomly may be used. For random keys, lengths
        // of from 4 to 16 bytes are recommended, depending on how
        // secure you want this to be.

        int i;
        byte rsum;
        unsigned keypos;

        // Start with cards all in order, one of each.

        for (i=0;i<256;i++)
                cards[i] = i;

        // Swap the card at each position with some other card.

        keypos = 0;         // Start with first byte of user key.
        rsum = 0;
        for (i=255;i;i--)
                std::swap(cards[i], cards[keyrand(i, key, keysize, &rsum, &keypos)]);

        // Initialize the indices and data dependencies.
        // Indices are set to different values instead of all 0
        // to reduce what is known about the state of the cards
        // when the first byte is emitted.

        rotor = cards[1];
        ratchet = cards[3];
        avalanche = cards[5];
        last_plain = cards[7];
        last_cipher = cards[rsum];

        rsum = 0;
        keypos = 0;
}

SapphireBase::~SapphireBase()
{
        rotor = ratchet = avalanche = last_plain = last_cipher = 0;
}

void SapphireEncryption::ProcessString(byte *outString, const byte *inString, unsigned int length)
{
        while(length--)
                *outString++ = SapphireEncryption::ProcessByte(*inString++);
}

void SapphireEncryption::ProcessString(byte *inoutString, unsigned int length)
{
        while(length--)
                *inoutString++ = SapphireEncryption::ProcessByte(*inoutString);
}

void SapphireDecryption::ProcessString(byte *outString, const byte *inString, unsigned int length)
{
        while(length--)
                *outString++ = SapphireDecryption::ProcessByte(*inString++);
}

void SapphireDecryption::ProcessString(byte *inoutString, unsigned int length)
{
        while(length--)
                *inoutString++ = SapphireDecryption::ProcessByte(*inoutString);
}

SapphireHash::SapphireHash(unsigned int hashLength)
        : SapphireEncryption(), hashLength(hashLength)
{
        // This function is used to initialize non-keyed hash
        // computation.

        int i, j;

        // Initialize the indices and data dependencies.

        rotor = 1;
        ratchet = 3;
        avalanche = 5;
        last_plain = 7;
        last_cipher = 11;

        // Start with cards all in inverse order.

        for (i=0, j=255;i<256;i++,j--)
                cards[i] = (byte) j;
}

void SapphireHash::Update(const byte *input, unsigned int length)
{
        while(length--)
                SapphireEncryption::ProcessByte(*input++);
}

void SapphireHash::Final(byte *hash, unsigned int overrideHashLength)
{
        for (int i=255; i>=0; i--)
                ProcessByte((byte) i);

        for (unsigned int j=0; j<overrideHashLength; j++)
                hash[j] = ProcessByte(0);
}

NAMESPACE_END

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