# SVC_SHA1Init

## Syntax

      #include <twl/os/common/systemCall.h>

      void SVC_SHA1Init( SVCSHA1Context* context );

  `typedef struct SVCSHA1Context
  {
  u32 h0,h1,h2,h3,h4;
  u32 Nl,Nh;
  u32 data[16];
  int num;
  void (*sha_block)(struct SVCSHA1Context *c, const u8 *W, int num);
  }
  SVCSHA1Context;`

## Arguments

context | Pointer to the context structure to initialize. This structure is used for SHA-1 generation.

## Return Values

None.

## Description

Initializes the structure to use when calculating SHA-1. Make sure this function is called before using the `SVC_SHA1Update` or `SVC_SHA1GetHash` functions.

context is the context structure to initialize for SHA-1 generation. You can reapply this function to a context structure that is already initialized. In this case, it will return the context structure to its initial state.

SHA-1 is an algorithm to find the message digest value. For details, see RFC (Request For Comments) 3174, which is published by IETF (the Internet Engineering Task Force).

## See Also

`SVC_SHA1Update`, `SVC_SHA1GetHash`

## Revision History

2007/10/19 Initial version.

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