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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
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2 * |
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3 * LibTomCrypt is a library that provides various cryptographic |
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4 * algorithms in a highly modular and flexible manner. |
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5 * |
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6 * The library is free for all purposes without any express |
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7 * guarantee it works. |
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8 * |
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9 * Tom St Denis, [email protected], http://libtomcrypt.org |
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10 */ |
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11 #include "tomcrypt.h" |
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12 |
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13 /** |
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14 @file der_length_bit_string.c |
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15 ASN.1 DER, get length of BIT STRING, Tom St Denis |
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16 */ |
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17 |
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18 #ifdef LTC_DER |
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19 /** |
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20 Gets length of DER encoding of BIT STRING |
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21 @param nbits The number of bits in the string to encode |
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22 @param outlen [out] The length of the DER encoding for the given string |
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23 @return CRYPT_OK if successful |
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24 */ |
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25 int der_length_bit_string(unsigned long nbits, unsigned long *outlen) |
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26 { |
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27 unsigned long nbytes; |
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28 LTC_ARGCHK(outlen != NULL); |
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29 |
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30 /* get the number of the bytes */ |
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31 nbytes = (nbits >> 3) + ((nbits & 7) ? 1 : 0) + 1; |
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32 |
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33 if (nbytes < 128) { |
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34 /* 03 LL PP DD DD DD ... */ |
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35 *outlen = 2 + nbytes; |
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36 } else if (nbytes < 256) { |
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37 /* 03 81 LL PP DD DD DD ... */ |
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38 *outlen = 3 + nbytes; |
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39 } else if (nbytes < 65536) { |
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40 /* 03 82 LL LL PP DD DD DD ... */ |
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41 *outlen = 4 + nbytes; |
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42 } else { |
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43 return CRYPT_INVALID_ARG; |
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44 } |
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45 |
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46 return CRYPT_OK; |
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47 } |
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48 |
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49 #endif |
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50 |
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51 |
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52 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_length_bit_string.c,v $ */ |
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53 /* $Revision: 1.1 $ */ |
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54 /* $Date: 2005/05/16 15:08:11 $ */ |
