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<concept id="GUID-48DB00D7-3807-5B4B-B4CE-D8C05B42CA6D" xml:lang="en"><title>Cryptography library</title><prolog><metadata><keywords/></metadata></prolog><conbody><p> <b>Changes since v7.0</b>  </p> <p>The Cryptography library is a new component that is based on Symbian-developed code rather than code licensed from RSA. It replaces the <codeph>cryptalg</codeph> and <codeph>privkey</codeph> variants (<filepath>cryptX.dll</filepath>, <filepath>privX.dll</filepath>) with a new <filepath>cryptography.dll</filepath>, which at present can be built in a weak or strong form: <filepath>weak_cryptography.dll</filepath> and <filepath>strong_cryptography.dll</filepath>. The weak version is limited to symmetric cryptographic operations with a maximum key size of 56 bits and asymmetric cryptographic operations with a maximum key size of 512 bits. Clients always link against <filepath>cryptography.dll</filepath>. </p> <p>On hardware, the version used is determined at ROM build time by including the appropriate version of the Cryptography library as <filepath>cryptography.dll</filepath>. On the emulator, the crypto switch sub-component supplies <filepath>cryptography.dll</filepath>, and this transparently forwards calls to the appropriate version of the Cryptography library. This setup allows a version of the emulator to be built that is not export restricted (including only the weak Cryptography library), which can be enhanced to use the strong crypto library merely by the addition of the appropriate DLL. </p> <p>Note that the new Cryptography deliverable (incorporating supporting libraries such as <filepath>hash.dll</filepath>) is not source or binary compatible with the previous <codeph>Cryptalg</codeph> implementation. </p> <p>The new Cryptography library has also been made available to the Symbian OS v7.0s release. </p> </conbody></concept>