1 | =pod
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2 |
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3 | =head1 NAME
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4 |
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5 | life_cycle-digest - The digest algorithm life-cycle
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6 |
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7 | =head1 DESCRIPTION
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8 |
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9 | All message digests (MDs) go through a number of stages in their life-cycle:
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10 |
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11 | =over 4
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12 |
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13 | =item start
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14 |
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15 | This state represents the MD before it has been allocated. It is the
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16 | starting state for any life-cycle transitions.
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17 |
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18 | =item newed
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19 |
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20 | This state represents the MD after it has been allocated.
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21 |
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22 | =item initialised
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23 |
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24 | This state represents the MD when it is set up and capable of processing
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25 | input.
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26 |
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27 | =item updated
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28 |
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29 | This state represents the MD when it is set up and capable of processing
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30 | additional input or generating output.
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31 |
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32 | =item finaled
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33 |
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34 | This state represents the MD when it has generated output.
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35 |
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36 | =item freed
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37 |
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38 | This state is entered when the MD is freed. It is the terminal state
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39 | for all life-cycle transitions.
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40 |
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41 | =back
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42 |
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43 | =head2 State Transition Diagram
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44 |
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45 | The usual life-cycle of a MD is illustrated:
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46 |
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47 | =begin man
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48 |
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49 | +-------------------+
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50 | | start |
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51 | +-------------------+
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52 | |
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53 | | EVP_MD_CTX_new
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54 | v
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55 | +-------------------+ EVP_MD_CTX_reset
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56 | | newed | <------------------------------+
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57 | +-------------------+ |
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58 | | |
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59 | | EVP_DigestInit |
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60 | v |
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61 | +-------------------+ |
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62 | +--> | initialised | <+ EVP_DigestInit |
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63 | | +-------------------+ | |
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64 | | | | EVP_DigestUpdate |
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65 | | | EVP_DigestUpdate | +------------------+ |
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66 | | v | v | |
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67 | | +------------------------------------------------+ |
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68 | EVP_DigestInit | | updated | --+
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69 | | +------------------------------------------------+ |
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70 | | | | |
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71 | | | EVP_DigestFinal | EVP_DigestFinalXOF |
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72 | | v v |
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73 | | +------------------------------------------------+ |
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74 | +--- | finaled | --+
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75 | +------------------------------------------------+
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76 | |
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77 | | EVP_MD_CTX_free
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78 | v
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79 | +-------------------+
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80 | | freed |
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81 | +-------------------+
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82 |
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83 | =end man
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84 |
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85 | =for html <img src="img/digest.png">
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86 |
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87 | =head2 Formal State Transitions
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88 |
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89 | This section defines all of the legal state transitions.
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90 | This is the canonical list.
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91 |
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92 | =begin man
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93 |
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94 | Function Call --------------------- Current State ----------------------
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95 | start newed initialised updated finaled freed
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96 | EVP_MD_CTX_new newed
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97 | EVP_DigestInit initialised initialised initialised initialised
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98 | EVP_DigestUpdate updated updated
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99 | EVP_DigestFinal finaled
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100 | EVP_DigestFinalXOF finaled
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101 | EVP_MD_CTX_free freed freed freed freed freed
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102 | EVP_MD_CTX_reset newed newed newed newed
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103 | EVP_MD_CTX_get_params newed initialised updated
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104 | EVP_MD_CTX_set_params newed initialised updated
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105 | EVP_MD_CTX_gettable_params newed initialised updated
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106 | EVP_MD_CTX_settable_params newed initialised updated
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107 |
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108 | =end man
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109 |
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110 | =begin html
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111 |
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112 | <table style="border:1px solid; border-collapse:collapse">
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113 | <tr><th style="border:1px solid" align="left">Function Call</th>
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114 | <th style="border:1px solid" colspan="6">Current State</th></tr>
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115 | <tr><th style="border:1px solid"></th>
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116 | <th style="border:1px solid" align="center">start</th>
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117 | <th style="border:1px solid" align="center">newed</th>
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118 | <th style="border:1px solid" align="center">initialised</th>
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119 | <th style="border:1px solid" align="center">updated</th>
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120 | <th style="border:1px solid" align="center">finaled</th>
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121 | <th style="border:1px solid" align="center">freed</th></tr>
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122 | <tr><th style="border:1px solid" align="left">EVP_MD_CTX_new</th>
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123 | <td style="border:1px solid" align="center">newed</td>
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124 | <td style="border:1px solid" align="center"></td>
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125 | <td style="border:1px solid" align="center"></td>
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126 | <td style="border:1px solid" align="center"></td>
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127 | <td style="border:1px solid" align="center"></td>
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128 | <td style="border:1px solid" align="center"></td></tr>
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129 | <tr><th style="border:1px solid" align="left">EVP_DigestInit</th>
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130 | <td style="border:1px solid" align="center"></td>
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131 | <td style="border:1px solid" align="center">initialised</td>
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132 | <td style="border:1px solid" align="center">initialised</td>
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133 | <td style="border:1px solid" align="center">initialised</td>
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134 | <td style="border:1px solid" align="center">initialised</td>
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135 | <td style="border:1px solid" align="center"></td></tr>
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136 | <tr><th style="border:1px solid" align="left">EVP_DigestUpdate</th>
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137 | <td style="border:1px solid" align="center"></td>
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138 | <td style="border:1px solid" align="center"></td>
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139 | <td style="border:1px solid" align="center">updated</td>
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140 | <td style="border:1px solid" align="center">updated</td>
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141 | <td style="border:1px solid" align="center"></td>
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142 | <td style="border:1px solid" align="center"></td></tr>
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143 | <tr><th style="border:1px solid" align="left">EVP_DigestFinal</th>
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144 | <td style="border:1px solid" align="center"></td>
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145 | <td style="border:1px solid" align="center"></td>
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146 | <td style="border:1px solid" align="center"></td>
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147 | <td style="border:1px solid" align="center">finaled</td>
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148 | <td style="border:1px solid" align="center"></td>
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149 | <td style="border:1px solid" align="center"></td></tr>
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150 | <tr><th style="border:1px solid" align="left">EVP_DigestFinalXOF</th>
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151 | <td style="border:1px solid" align="center"></td>
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152 | <td style="border:1px solid" align="center"></td>
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153 | <td style="border:1px solid" align="center"></td>
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154 | <td style="border:1px solid" align="center">finaled</td>
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155 | <td style="border:1px solid" align="center"></td>
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156 | <td style="border:1px solid" align="center"></td></tr>
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157 | <tr><th style="border:1px solid" align="left">EVP_MD_CTX_free</th>
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158 | <td style="border:1px solid" align="center">freed</td>
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159 | <td style="border:1px solid" align="center">freed</td>
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160 | <td style="border:1px solid" align="center">freed</td>
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161 | <td style="border:1px solid" align="center">freed</td>
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162 | <td style="border:1px solid" align="center">freed</td>
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163 | <td style="border:1px solid" align="center"></td></tr>
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164 | <tr><th style="border:1px solid" align="left">EVP_MD_CTX_reset</th>
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165 | <td style="border:1px solid" align="center"></td>
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166 | <td style="border:1px solid" align="center">newed</td>
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167 | <td style="border:1px solid" align="center">newed</td>
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168 | <td style="border:1px solid" align="center">newed</td>
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169 | <td style="border:1px solid" align="center">newed</td>
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170 | <td style="border:1px solid" align="center"></td></tr>
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171 | <tr><th style="border:1px solid" align="left">EVP_MD_CTX_get_params</th>
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172 | <td style="border:1px solid" align="center"></td>
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173 | <td style="border:1px solid" align="center">newed</td>
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174 | <td style="border:1px solid" align="center">initialised</td>
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175 | <td style="border:1px solid" align="center">updated</td>
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176 | <td style="border:1px solid" align="center"></td>
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177 | <td style="border:1px solid" align="center"></td></tr>
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178 | <tr><th style="border:1px solid" align="left">EVP_MD_CTX_set_params</th>
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179 | <td style="border:1px solid" align="center"></td>
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180 | <td style="border:1px solid" align="center">newed</td>
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181 | <td style="border:1px solid" align="center">initialised</td>
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182 | <td style="border:1px solid" align="center">updated</td>
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183 | <td style="border:1px solid" align="center"></td>
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184 | <td style="border:1px solid" align="center"></td></tr>
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185 | <tr><th style="border:1px solid" align="left">EVP_MD_CTX_gettable_params</th>
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186 | <td style="border:1px solid" align="center"></td>
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187 | <td style="border:1px solid" align="center">newed</td>
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188 | <td style="border:1px solid" align="center">initialised</td>
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189 | <td style="border:1px solid" align="center">updated</td>
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190 | <td style="border:1px solid" align="center"></td>
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191 | <td style="border:1px solid" align="center"></td></tr>
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192 | <tr><th style="border:1px solid" align="left">EVP_MD_CTX_settable_params</th>
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193 | <td style="border:1px solid" align="center"></td>
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194 | <td style="border:1px solid" align="center">newed</td>
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195 | <td style="border:1px solid" align="center">initialised</td>
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196 | <td style="border:1px solid" align="center">updated</td>
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197 | <td style="border:1px solid" align="center"></td>
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198 | <td style="border:1px solid" align="center"></td></tr>
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199 | </table>
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200 |
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201 | =end html
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202 |
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203 | =head1 NOTES
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204 |
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205 | At some point the EVP layer will begin enforcing the transitions described
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206 | herein.
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207 |
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208 | =head1 SEE ALSO
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209 |
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210 | L<provider-digest(7)>, L<EVP_DigestInit(3)>
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211 |
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212 | =head1 COPYRIGHT
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213 |
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214 | Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
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215 |
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216 | Licensed under the Apache License 2.0 (the "License"). You may not use
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217 | this file except in compliance with the License. You can obtain a copy
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218 | in the file LICENSE in the source distribution or at
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219 | L<https://www.openssl.org/source/license.html>.
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220 |
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221 | =cut
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