diff --git a/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/nfold.go b/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/nfold.go
new file mode 100644
index 0000000..779d1c6
--- /dev/null
+++ b/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/nfold.go
@@ -0,0 +1,128 @@
+package rfc3961
+
+/*
+Implementation of the n-fold algorithm as defined in RFC 3961.
+
+n-fold is an algorithm that takes m input bits and "stretches" them
+to form n output bits with equal contribution from each input bit to
+the output, as described in [Blumenthal96]:
+
+We first define a primitive called n-folding, which takes a
+variable-length input block and produces a fixed-length output
+sequence.  The intent is to give each input bit approximately
+equal weight in determining the value of each output bit.  Note
+that whenever we need to treat a string of octets as a number, the
+assumed representation is Big-Endian -- Most Significant Byte
+first.
+
+To n-fold a number X, replicate the input value to a length that
+is the least common multiple of n and the length of X.  Before
+each repetition, the input is rotated to the right by 13 bit
+positions.  The successive n-bit chunks are added together using
+1's-complement addition (that is, with end-around carry) to yield
+a n-bit result....
+*/
+
+/* Credits
+This golang implementation of nfold used the following project for help with implementation detail.
+Although their source is in java it was helpful as a reference implementation of the RFC.
+You can find the source code of their open source project along with license information below.
+We acknowledge and are grateful to these developers for their contributions to open source
+
+Project: Apache Directory (http://http://directory.apache.org/)
+https://svn.apache.org/repos/asf/directory/apacheds/tags/1.5.1/kerberos-shared/src/main/java/org/apache/directory/server/kerberos/shared/crypto/encryption/NFold.java
+License: http://www.apache.org/licenses/LICENSE-2.0
+*/
+
+// Nfold expands the key to ensure it is not smaller than one cipher block.
+// Defined in RFC 3961.
+//
+// m input bytes that will be "stretched" to the least common multiple of n bits and the bit length of m.
+func Nfold(m []byte, n int) []byte {
+	k := len(m) * 8
+
+	//Get the lowest common multiple of the two bit sizes
+	lcm := lcm(n, k)
+	relicate := lcm / k
+	var sumBytes []byte
+
+	for i := 0; i < relicate; i++ {
+		rotation := 13 * i
+		sumBytes = append(sumBytes, rotateRight(m, rotation)...)
+	}
+
+	nfold := make([]byte, n/8)
+	sum := make([]byte, n/8)
+	for i := 0; i < lcm/n; i++ {
+		for j := 0; j < n/8; j++ {
+			sum[j] = sumBytes[j+(i*len(sum))]
+		}
+		nfold = onesComplementAddition(nfold, sum)
+	}
+	return nfold
+}
+
+func onesComplementAddition(n1, n2 []byte) []byte {
+	numBits := len(n1) * 8
+	out := make([]byte, numBits/8)
+	carry := 0
+	for i := numBits - 1; i > -1; i-- {
+		n1b := getBit(&n1, i)
+		n2b := getBit(&n2, i)
+		s := n1b + n2b + carry
+
+		if s == 0 || s == 1 {
+			setBit(&out, i, s)
+			carry = 0
+		} else if s == 2 {
+			carry = 1
+		} else if s == 3 {
+			setBit(&out, i, 1)
+			carry = 1
+		}
+	}
+	if carry == 1 {
+		carryArray := make([]byte, len(n1))
+		carryArray[len(carryArray)-1] = 1
+		out = onesComplementAddition(out, carryArray)
+	}
+	return out
+}
+
+func rotateRight(b []byte, step int) []byte {
+	out := make([]byte, len(b))
+	bitLen := len(b) * 8
+	for i := 0; i < bitLen; i++ {
+		v := getBit(&b, i)
+		setBit(&out, (i+step)%bitLen, v)
+	}
+	return out
+}
+
+func lcm(x, y int) int {
+	return (x * y) / gcd(x, y)
+}
+
+func gcd(x, y int) int {
+	for y != 0 {
+		x, y = y, x%y
+	}
+	return x
+}
+
+func getBit(b *[]byte, p int) int {
+	pByte := p / 8
+	pBit := uint(p % 8)
+	vByte := (*b)[pByte]
+	vInt := int(vByte >> (8 - (pBit + 1)) & 0x0001)
+	return vInt
+}
+
+func setBit(b *[]byte, p, v int) {
+	pByte := p / 8
+	pBit := uint(p % 8)
+	oldByte := (*b)[pByte]
+	var newByte byte
+	newByte = byte(v<<(8-(pBit+1))) | oldByte
+	(*b)[pByte] = newByte
+}