week1

aes/aes.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"crypto/aes"
+	"encoding/hex"
+	"fmt"
+)
+
+func main() {
+
+	// cipher key
+	key := "thisis32bitlongpassphraseimusing"
+
+	// plaintext
+	pt := "This is a secret"
+
+	c := EncryptAES([]byte(key), pt)
+
+	// plaintext
+	fmt.Println((pt))
+
+	fmt.Println([]byte(pt))
+
+	// ciphertext
+
+	fmt.Println((c))
+	fmt.Println([]byte(c))
+
+	key2 := "thisis32bitlongpassphraseimusing"
+
+	// decrypt
+	DecryptAES([]byte(key2), c)
+}
+
+func EncryptAES(key []byte, plaintext string) string {
+
+	c, err := aes.NewCipher(key)
+	CheckError(err)
+
+	out := make([]byte, len(plaintext))
+
+	c.Encrypt(out, []byte(plaintext))
+
+	return hex.EncodeToString(out)
+}
+
+func DecryptAES(key []byte, ct string) {
+	ciphertext, _ := hex.DecodeString(ct)
+
+	c, err := aes.NewCipher(key)
+	CheckError(err)
+
+	pt := make([]byte, len(ciphertext))
+	c.Decrypt(pt, ciphertext)
+
+	s := string(pt[:])
+	fmt.Println("DECRYPTED:", s)
+}
+
+func CheckError(err error) {
+	if err != nil {
+		panic(err)
+	}
+}

hashing/hashing-examples.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"crypto/md5"
+	"crypto/sha256"
+	"fmt"
+)
+
+func main() {
+	s := "Hello"
+
+	sha256 := sha256.Sum256([]byte(s))
+	md5 := md5.Sum([]byte(s))
+
+	fmt.Println()
+	fmt.Println(s)
+
+	fmt.Println()
+	fmt.Printf("%x", sha256)
+	fmt.Println()
+
+	fmt.Println()
+	fmt.Printf("%x", md5)
+
+	fmt.Println()
+	fmt.Println()
+
+}

rsa/rsa-encrypt-sign.go

@@ -0,0 +1,137 @@
+// Derived from: https://medium.com/@bobgzm/golang-cryptography-rsa-asymmetric-algorithm-e91363a2f7b3
+
+package main
+
+import (
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"fmt"
+	"os"
+)
+
+func main() {
+
+	alicePrivateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	alicePublicKey := &alicePrivateKey.PublicKey
+
+	trudyPrivateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	//trudyPublicKey := &trudyPrivateKey.PublicKey
+
+	bobPrivateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	bobPublicKey := &bobPrivateKey.PublicKey
+
+	fmt.Println("Alice's Private Key : ", alicePrivateKey)
+	fmt.Println()
+	fmt.Println("Alice's Public key ", alicePublicKey)
+	fmt.Println()
+	fmt.Println("Bob's Private Key : ", bobPrivateKey)
+	fmt.Println()
+	fmt.Println("Bob's Public key ", bobPublicKey)
+	fmt.Println()
+
+	message := []byte("first rule of cs5970 is that you tell everyone about cs5970")
+	label := []byte("")
+	hash := sha256.New()
+
+	// RSA encryption examples
+	ciphertext, err := rsa.EncryptOAEP(
+		hash,
+		rand.Reader,
+		bobPublicKey,
+		message,
+		label)
+
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	// OAEP is a padding scheme, used with RSA
+	fmt.Printf("OAEP encrypted [%s] to \n[%x]\n", string(message), ciphertext)
+	fmt.Println()
+
+	// Same encryption, but ciphertext2 will be different due to rand.Reader
+	ciphertext2, err := rsa.EncryptOAEP(
+		hash,
+		rand.Reader,
+		bobPublicKey,
+		message,
+		label)
+
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	// OAEP is a padding scheme, used with RSA
+	fmt.Printf("OAEP encrypted [%s] to \n[%x]\n", string(message), ciphertext2)
+	fmt.Println()
+
+	// Digital signature examples
+	var opts rsa.PSSOptions
+	opts.SaltLength = rsa.PSSSaltLengthAuto // for simple example
+	PSSmessage := message
+	newhash := crypto.SHA256
+	pssh := newhash.New()
+	pssh.Write(PSSmessage)
+
+	hashed := pssh.Sum(nil)
+	signature, err := rsa.SignPSS(
+		rand.Reader,
+		trudyPrivateKey,
+		newhash,
+		hashed,
+		&opts)
+
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	// Probabilistic Signature Scheme (PSS)
+	fmt.Printf("PSS Signature : %x\n", signature)
+	fmt.Println()
+
+	plainText, err := rsa.DecryptOAEP(
+		hash,
+		rand.Reader,
+		bobPrivateKey,
+		ciphertext,
+		label)
+
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("OAEP decrypted [%x] to \n[%s]\n", ciphertext, plainText)
+	fmt.Println()
+
+	err = rsa.VerifyPSS(
+		alicePublicKey,
+		newhash,
+		hashed,
+		signature,
+		&opts)
+
+	if err != nil {
+		fmt.Println("Signature verification failed!")
+		os.Exit(1)
+	} else {
+		fmt.Println("Signature verification successful!")
+	}
+}