Hash Functions

Functions featured in this section apply hash algorithms to digesting streaming messages. A primitive implementing a hash algorithm uses the state context (for example, ippsSHA1State) as an operational vehicle to carry all necessary variables to manage the computation of the chaining digest value. For example, the primitive implementing the SHA-1 hash algorithm must use the ippsSHA1State context.

The function Init initializes (MD5Init, SHA1Init, SHA224Init, SHA256Init, SHA384Init, and SHA512Init) the context and sets up specified initialization vectors. Once initialized, the function Update (MD5Update, SHA1Update, SHA224Update, SHA256Update, SHA384Update, and SHA512Update) digests the input message stream with the selected hash algorithm till it exhausts all message blocks. The function Final (MD5Final, SHA1Final, SHA224Final, SHA256Final, SHA384Final, and SHA512Final) is designed to pad the partial message block into a final message block with the specified padding scheme, and then uses the hash algorithm to transform the final block into a message digest value.

The following example illustrates how the application code can apply the implemented SHA-1 hash standard to digest the input message stream.

1. Call the function SHA1GetSize to get the size required to configure the ippsSHA1State context.

2. Ensure that the required memory space is properly allocated. With the allocated memory, call the SHA1Init function to set up the initial context state with the SHA-1 specified initialization vectors.

3. Keep calling the function SHA1Update to digest incoming message stream in the queue till its completion. To determine the current value of the digest, call SHA1GetTag between the two calls to SHA1Update.

4. Call the function SHA1Final for padding the partial block into a final SHA-1 message block and transforming it into a 160-bit message digest value.

5. Call the operating system memory free service function to release the ippsSHA1State context.

The contexts used by the hash primitives (for example, ippsSHA1State) are position-dependent. The following functions transform the respective position-dependent context to a position-independent form and vice versa:

• SHA1Pack/SHA1Unpack

• SHA224Pack/SHA224Unpack

• SHA256Pack/SHA256Unpack

• SHA384Pack/SHA384Unpack

• SHA512Pack/SHA512Unpack

• MD5Pack/MD5Unpack

• MD5GetSize
  Gets the size of the IppsMD5State context in bytes.
• MD5Init
  Initializes user-supplied memory as IppsMD5State context for future use.
• MD5Pack, MD5Unpack
  Packs/unpacks the IppsMD5State context into/from a user-defined buffer.
• MD5Duplicate
  Copies one IppsMD5State context to another.
• MD5Update
  Digests the current input message stream of the specified length.
• MD5Final
  Completes computation of the MD5 digest value.
• MD5GetTag
  Computes the current MD5 digest value of the processed part of the message.
• SHA1GetSize
  Gets the size of the IppsSHA1State context in bytes.
• SHA1Init
  Initializes user-supplied memory as IppsSHA1State context for future use.
• SHA1Pack, SHA1Unpack
  Packs/unpacks the IppsSHA1State context into/from a user-defined buffer.
• SHA1Duplicate
  Copies one IppsSHA1State context to another.
• SHA1Update
  Digests the current input message stream of the specified length.
• SHA1Final
  Completes computation of the SHA-1 digest value.
• SHA1GetTag
  Computes the current SHA-1 digest value of the processed part of the message.
• SHA224GetSize
  Gets the size of the IppsSHA224State context in bytes.
• SHA224Init
  Initializes user-supplied memory as IppsSHA224State context for future use.
• SHA224Pack, SHA224Unpack
  Packs/unpacks the IppsSHA224State context into/from a user-defined buffer.
• SHA224Duplicate
  Copies one IppsSHA224State context to another.
• SHA224Update
  Digests the current input message stream of the specified length.
• SHA224Final
  Completes computation of the SHA-224 digest value.
• SHA224GetTag
  Computes the current SHA-224 digest value of the processed part of the message.
• SHA256GetSize
  Gets the size of the IppsSHA256State context in bytes.
• SHA256Init
  Initializes user-supplied memory as IppsSHA256State context for future use.
• SHA256Pack, SHA256Unpack
  Packs/unpacks the IppsSHA256State context into/from a user-defined buffer.
• SHA256Duplicate
  Copies one IppsSHA256State context to another.
• SHA256Update
  Digests the current input message stream of the specified length.
• SHA256Final
  Completes computation of the SHA-256 digest value.
• SHA256GetTag
  Computes the current SHA-256 digest value of the processed part of the message.
• SHA384GetSize
  Gets the size of the IppsSHA384State context in bytes.
• SHA384Init
  Initializes user-supplied memory as IppsSHA384State context for future use.
• SHA384Pack, SHA384Unpack
  Packs/unpacks the IppsSHA384State context into/from a user-defined buffer.
• SHA384Duplicate
  Copies one IppsSHA384State context to another.
• SHA384Update
  Digests the current input message stream of the specified length.
• SHA384Final
  Completes computing of the SHA-384 digest value.
• SHA384GetTag
  Computes the current SHA-384 digest value of the processed part of the message.
• SHA512GetSize
  Gets the size of the IppsSHA512State context in bytes.
• SHA512Init
  Initializes user-supplied memory as IppsSHA512State context for future use.
• SHA512Pack, SHA512Unpack
  Packs/unpacks the IppsSHA512State context into/from a user-defined buffer.
• SHA512Duplicate
  Copies one IppsSHA512State context to another.
• SHA512Update
  Digests the current input message stream of the specified length.
• SHA512Final
  Completes computation of the SHA-512 digest value.
• SHA512GetTag
  Computes the current SHA-512 digest value of the processed part of the message.

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