From 9918b6c84e2547f3d24a6cfeb97cfcbd6cb4dc98 Mon Sep 17 00:00:00 2001
From: Gustav Simonsson <gustav.simonsson@gmail.com>
Date: Thu, 2 Apr 2015 17:02:56 +0200
Subject: Remove the awesome, ever misunderstood entropy mixing

---
 crypto/randentropy/rand_entropy.go | 51 +-------------------------------------
 1 file changed, 1 insertion(+), 50 deletions(-)

(limited to 'crypto/randentropy/rand_entropy.go')

diff --git a/crypto/randentropy/rand_entropy.go b/crypto/randentropy/rand_entropy.go
index b87fa564e..68bb8808b 100644
--- a/crypto/randentropy/rand_entropy.go
+++ b/crypto/randentropy/rand_entropy.go
@@ -2,12 +2,8 @@ package randentropy
 
 import (
 	crand "crypto/rand"
-	"encoding/binary"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
 	"io"
-	"os"
-	"strings"
-	"time"
 )
 
 var Reader io.Reader = &randEntropy{}
@@ -16,7 +12,7 @@ type randEntropy struct {
 }
 
 func (*randEntropy) Read(bytes []byte) (n int, err error) {
-	readBytes := GetEntropyMixed(len(bytes))
+	readBytes := GetEntropyCSPRNG(len(bytes))
 	copy(bytes, readBytes)
 	return len(bytes), nil
 }
@@ -29,40 +25,6 @@ func Sha3(data []byte) []byte {
 	return d.Sum(nil)
 }
 
-// TODO: verify. this needs to be audited
-// we start with crypt/rand, then XOR in additional entropy from OS
-func GetEntropyMixed(n int) []byte {
-	startTime := time.Now().UnixNano()
-	// for each source, we take SHA3 of the source and use it as seed to math/rand
-	// then read bytes from it and XOR them onto the bytes read from crypto/rand
-	mainBuff := GetEntropyCSPRNG(n)
-	// 1. OS entropy sources
-	startTimeBytes := make([]byte, 32)
-	binary.PutVarint(startTimeBytes, startTime)
-	startTimeHash := Sha3(startTimeBytes)
-	mixBytes(mainBuff, startTimeHash)
-
-	pid := os.Getpid()
-	pidBytes := make([]byte, 32)
-	binary.PutUvarint(pidBytes, uint64(pid))
-	pidHash := Sha3(pidBytes)
-	mixBytes(mainBuff, pidHash)
-
-	osEnv := os.Environ()
-	osEnvBytes := []byte(strings.Join(osEnv, ""))
-	osEnvHash := Sha3(osEnvBytes)
-	mixBytes(mainBuff, osEnvHash)
-
-	// not all OS have hostname in env variables
-	osHostName, err := os.Hostname()
-	if err != nil {
-		osHostNameBytes := []byte(osHostName)
-		osHostNameHash := Sha3(osHostNameBytes)
-		mixBytes(mainBuff, osHostNameHash)
-	}
-	return mainBuff
-}
-
 func GetEntropyCSPRNG(n int) []byte {
 	mainBuff := make([]byte, n)
 	_, err := io.ReadFull(crand.Reader, mainBuff)
@@ -71,14 +33,3 @@ func GetEntropyCSPRNG(n int) []byte {
 	}
 	return mainBuff
 }
-
-func mixBytes(buff []byte, mixBuff []byte) []byte {
-	bytesToMix := len(buff)
-	if bytesToMix > 32 {
-		bytesToMix = 32
-	}
-	for i := 0; i < bytesToMix; i++ {
-		buff[i] ^= mixBuff[i]
-	}
-	return buff
-}
-- 
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