Start working on set 3, challenge 19

Author: robquant

challenge3_18.go

@@ -15,5 +15,5 @@ func main() {
 	key := []byte("YELLOW SUBMARINE")
 	nonce := uint64(0)
 	ciphertext, _ := base64.StdEncoding.DecodeString(ciphertextBase64)
-	fmt.Println(string(tools.EncryptAesCtr(ciphertext, key, nonce)))
+	fmt.Println(string(tools.DecryptAesCtr(ciphertext, key, nonce)))
 }

challenge3_19.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"bufio"
+	"encoding/base64"
+	"fmt"
+	"log"
+	"math/rand"
+	"os"
+	"time"
+
+	"github.com/robquant/cryptopals/pkg/tools"
+)
+
+func main() {
+	file, err := os.Open("input/input3_19.txt")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	key := make([]byte, 16)
+	rand.Seed(time.Now().UnixNano())
+	rand.Read(key)
+	nonce := uint64(0)
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		plaintext, _ := base64.StdEncoding.DecodeString(scanner.Text())
+		fmt.Println(tools.EncryptAesCtr(plaintext, key, nonce))
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+}

input/input3_19.txt

@@ -0,0 +1,40 @@
+SSBoYXZlIG1ldCB0aGVtIGF0IGNsb3NlIG9mIGRheQ==
+Q29taW5nIHdpdGggdml2aWQgZmFjZXM=
+RnJvbSBjb3VudGVyIG9yIGRlc2sgYW1vbmcgZ3JleQ==
+RWlnaHRlZW50aC1jZW50dXJ5IGhvdXNlcy4=
+SSBoYXZlIHBhc3NlZCB3aXRoIGEgbm9kIG9mIHRoZSBoZWFk
+T3IgcG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==
+T3IgaGF2ZSBsaW5nZXJlZCBhd2hpbGUgYW5kIHNhaWQ=
+UG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==
+QW5kIHRob3VnaHQgYmVmb3JlIEkgaGFkIGRvbmU=
+T2YgYSBtb2NraW5nIHRhbGUgb3IgYSBnaWJl
+VG8gcGxlYXNlIGEgY29tcGFuaW9u
+QXJvdW5kIHRoZSBmaXJlIGF0IHRoZSBjbHViLA==
+QmVpbmcgY2VydGFpbiB0aGF0IHRoZXkgYW5kIEk=
+QnV0IGxpdmVkIHdoZXJlIG1vdGxleSBpcyB3b3JuOg==
+QWxsIGNoYW5nZWQsIGNoYW5nZWQgdXR0ZXJseTo=
+QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=
+VGhhdCB3b21hbidzIGRheXMgd2VyZSBzcGVudA==
+SW4gaWdub3JhbnQgZ29vZCB3aWxsLA==
+SGVyIG5pZ2h0cyBpbiBhcmd1bWVudA==
+VW50aWwgaGVyIHZvaWNlIGdyZXcgc2hyaWxsLg==
+V2hhdCB2b2ljZSBtb3JlIHN3ZWV0IHRoYW4gaGVycw==
+V2hlbiB5b3VuZyBhbmQgYmVhdXRpZnVsLA==
+U2hlIHJvZGUgdG8gaGFycmllcnM/
+VGhpcyBtYW4gaGFkIGtlcHQgYSBzY2hvb2w=
+QW5kIHJvZGUgb3VyIHdpbmdlZCBob3JzZS4=
+VGhpcyBvdGhlciBoaXMgaGVscGVyIGFuZCBmcmllbmQ=
+V2FzIGNvbWluZyBpbnRvIGhpcyBmb3JjZTs=
+SGUgbWlnaHQgaGF2ZSB3b24gZmFtZSBpbiB0aGUgZW5kLA==
+U28gc2Vuc2l0aXZlIGhpcyBuYXR1cmUgc2VlbWVkLA==
+U28gZGFyaW5nIGFuZCBzd2VldCBoaXMgdGhvdWdodC4=
+VGhpcyBvdGhlciBtYW4gSSBoYWQgZHJlYW1lZA==
+QSBkcnVua2VuLCB2YWluLWdsb3Jpb3VzIGxvdXQu
+SGUgaGFkIGRvbmUgbW9zdCBiaXR0ZXIgd3Jvbmc=
+VG8gc29tZSB3aG8gYXJlIG5lYXIgbXkgaGVhcnQs
+WWV0IEkgbnVtYmVyIGhpbSBpbiB0aGUgc29uZzs=
+SGUsIHRvbywgaGFzIHJlc2lnbmVkIGhpcyBwYXJ0
+SW4gdGhlIGNhc3VhbCBjb21lZHk7
+SGUsIHRvbywgaGFzIGJlZW4gY2hhbmdlZCBpbiBoaXMgdHVybiw=
+VHJhbnNmb3JtZWQgdXR0ZXJseTo=
+QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=

pkg/tools/aes.go

@@ -132,6 +132,10 @@ func (ks *AesCtrKeyStream) NextByte() byte {
 	return b
 }
 
+func (ks *AesCtrKeyStream) Reset() {
+	ks.byteCounter = 0
+}
+
 func EncryptAesCtr(plaintext, key []byte, nonce uint64) []byte {
 	ks := NewAesCtrKeyStream(key, nonce)
 	return ctrStream(plaintext, ks)