github.com/bartle-stripe/trillian@v1.2.1/testonly/hasher.go (about)

     1  // Copyright 2017 Google Inc. All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package testonly
    16  
    17  // This file implements the hashing functions that are part of a Trillian
    18  // personality.
    19  
    20  import (
    21  	"crypto/sha256"
    22  )
    23  
    24  // HashKey converts a map key into a map index using SHA256.
    25  // This preserves tests that precomputed indexes based on SHA256.
    26  func HashKey(key string) []byte {
    27  	h := sha256.New()
    28  	h.Write([]byte(key))
    29  	return h.Sum(nil)
    30  }
    31  
    32  // TransparentHash returns a key that can be visually inspected.
    33  // This supports testing where it was nice to see what the key was.
    34  func TransparentHash(key string) []byte {
    35  	const prefixLen = 8
    36  	if prefixLen+len(key) > sha256.Size {
    37  		panic("key too long")
    38  	}
    39  	b := make([]byte, sha256.Size)
    40  	// Put some hashed bytes before the key so that key values are
    41  	// a bit more widely distributed around the Merkle tree.
    42  	h := HashKey(key)
    43  	copy(b[0:prefixLen], h[0:prefixLen])
    44  	copy(b[prefixLen:], key)
    45  	return b
    46  }