constant_time.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package subtle implements functions that are often useful in cryptographic
     6  // code but require careful thought to use correctly.
     7  package subtle
     8  
     9  import "crypto/internal/fips140/subtle"
    10  
    11  // ConstantTimeCompare returns 1 if the two slices, x and y, have equal contents
    12  // and 0 otherwise. The time taken is a function of the length of the slices and
    13  // is independent of the contents. If the lengths of x and y do not match it
    14  // returns 0 immediately.
    15  func ConstantTimeCompare(x, y []byte) int {
    16  	return subtle.ConstantTimeCompare(x, y)
    17  }
    18  
    19  // ConstantTimeSelect returns x if v == 1 and y if v == 0.
    20  // Its behavior is undefined if v takes any other value.
    21  func ConstantTimeSelect(v, x, y int) int {
    22  	return subtle.ConstantTimeSelect(v, x, y)
    23  }
    24  
    25  // ConstantTimeByteEq returns 1 if x == y and 0 otherwise.
    26  func ConstantTimeByteEq(x, y uint8) int {
    27  	return subtle.ConstantTimeByteEq(x, y)
    28  }
    29  
    30  // ConstantTimeEq returns 1 if x == y and 0 otherwise.
    31  func ConstantTimeEq(x, y int32) int {
    32  	return subtle.ConstantTimeEq(x, y)
    33  }
    34  
    35  // ConstantTimeCopy copies the contents of y into x (a slice of equal length)
    36  // if v == 1. If v == 0, x is left unchanged. Its behavior is undefined if v
    37  // takes any other value.
    38  func ConstantTimeCopy(v int, x, y []byte) {
    39  	subtle.ConstantTimeCopy(v, x, y)
    40  }
    41  
    42  // ConstantTimeLessOrEq returns 1 if x <= y and 0 otherwise.
    43  // Its behavior is undefined if x or y are negative or > 2**31 - 1.
    44  func ConstantTimeLessOrEq(x, y int) int {
    45  	return subtle.ConstantTimeLessOrEq(x, y)
    46  }
    47
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