github.com/adnan-c/fabric_e2e_couchdb@v0.6.1-preview.0.20170228180935-21ce6b23cf91/core/crypto/primitives/hash.go (about)

     1  /*
     2  Copyright IBM Corp. 2016 All Rights Reserved.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8  		 http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package primitives
    18  
    19  import (
    20  	"crypto/hmac"
    21  	"hash"
    22  )
    23  
    24  var (
    25  	defaultHash          func() hash.Hash
    26  	defaultHashAlgorithm string
    27  )
    28  
    29  // GetDefaultHash returns the default hash function used by the crypto layer
    30  func GetDefaultHash() func() hash.Hash {
    31  	return defaultHash
    32  }
    33  
    34  // GetHashAlgorithm return the default hash algorithm
    35  func GetHashAlgorithm() string {
    36  	return defaultHashAlgorithm
    37  }
    38  
    39  // NewHash returns a new hash function
    40  func NewHash() hash.Hash {
    41  	return GetDefaultHash()()
    42  }
    43  
    44  // Hash hashes the msh using the predefined hash function
    45  func Hash(msg []byte) []byte {
    46  	h := NewHash()
    47  	h.Write(msg)
    48  	return h.Sum(nil)
    49  }
    50  
    51  // HMACTruncated hmacs x using key key and truncate to truncation
    52  func HMACTruncated(key, x []byte, truncation int) []byte {
    53  	mac := hmac.New(GetDefaultHash(), key)
    54  	mac.Write(x)
    55  
    56  	return mac.Sum(nil)[:truncation]
    57  }