CAST5 vector creation¶
This page documents the code that was used to generate the CAST5 CBC, CFB, OFB, and CTR test vectors as well as the code used to verify them against another implementation. The CBC, CFB, and OFB vectors were generated using OpenSSL and the CTR vectors were generated using Apple’s CommonCrypto. All the generated vectors were verified with Go.
Creation¶
cryptography was modified to support CAST5 in CBC, CFB, and OFB modes. Then
the following Python script was run to generate the vector files.
# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
import binascii
from cryptography.hazmat.primitives.ciphers import algorithms, base, modes
def encrypt(mode, key, iv, plaintext):
cipher = base.Cipher(
algorithms.CAST5(binascii.unhexlify(key)),
mode(binascii.unhexlify(iv)),
)
encryptor = cipher.encryptor()
ct = encryptor.update(binascii.unhexlify(plaintext))
ct += encryptor.finalize()
return binascii.hexlify(ct)
def build_vectors(mode, filename):
count = 0
output = []
key = None
iv = None
plaintext = None
with open(filename, "r") as vector_file:
for line in vector_file:
line = line.strip()
if line.startswith("KEY"):
if count != 0:
output.append(
"CIPHERTEXT = {}".format(
encrypt(mode, key, iv, plaintext)
)
)
output.append("\nCOUNT = {}".format(count))
count += 1
name, key = line.split(" = ")
output.append("KEY = {}".format(key))
elif line.startswith("IV"):
name, iv = line.split(" = ")
iv = iv[0:16]
output.append("IV = {}".format(iv))
elif line.startswith("PLAINTEXT"):
name, plaintext = line.split(" = ")
output.append("PLAINTEXT = {}".format(plaintext))
output.append(
"CIPHERTEXT = {}".format(encrypt(mode, key, iv, plaintext))
)
return "\n".join(output)
def write_file(data, filename):
with open(filename, "w") as f:
f.write(data)
cbc_path = "tests/hazmat/primitives/vectors/ciphers/AES/CBC/CBCMMT128.rsp"
write_file(build_vectors(modes.CBC, cbc_path), "cast5-cbc.txt")
ofb_path = "tests/hazmat/primitives/vectors/ciphers/AES/OFB/OFBMMT128.rsp"
write_file(build_vectors(modes.OFB, ofb_path), "cast5-ofb.txt")
cfb_path = "tests/hazmat/primitives/vectors/ciphers/AES/CFB/CFB128MMT128.rsp"
write_file(build_vectors(modes.CFB, cfb_path), "cast5-cfb.txt")
ctr_path = "tests/hazmat/primitives/vectors/ciphers/AES/CTR/aes-128-ctr.txt"
write_file(build_vectors(modes.CTR, ctr_path), "cast5-ctr.txt")
Download link: generate_cast5.py
Verification¶
The following Go code was used to verify the vectors.
package main
import (
"bufio"
"bytes"
"golang.org/x/crypto/cast5"
"crypto/cipher"
"encoding/hex"
"fmt"
"os"
"strings"
)
func unhexlify(s string) []byte {
bytes, err := hex.DecodeString(s)
if err != nil {
panic(err)
}
return bytes
}
type vectorArgs struct {
count string
key string
iv string
plaintext string
ciphertext string
}
type vectorVerifier interface {
validate(count string, key, iv, plaintext, expectedCiphertext []byte)
}
type ofbVerifier struct{}
func (o ofbVerifier) validate(count string, key, iv, plaintext, expectedCiphertext []byte) {
block, err := cast5.NewCipher(key)
if err != nil {
panic(err)
}
ciphertext := make([]byte, len(plaintext))
stream := cipher.NewOFB(block, iv)
stream.XORKeyStream(ciphertext, plaintext)
if !bytes.Equal(ciphertext, expectedCiphertext) {
panic(fmt.Errorf("vector mismatch @ COUNT = %s:\n %s != %s\n",
count,
hex.EncodeToString(expectedCiphertext),
hex.EncodeToString(ciphertext)))
}
}
type cbcVerifier struct{}
func (o cbcVerifier) validate(count string, key, iv, plaintext, expectedCiphertext []byte) {
block, err := cast5.NewCipher(key)
if err != nil {
panic(err)
}
ciphertext := make([]byte, len(plaintext))
mode := cipher.NewCBCEncrypter(block, iv)
mode.CryptBlocks(ciphertext, plaintext)
if !bytes.Equal(ciphertext, expectedCiphertext) {
panic(fmt.Errorf("vector mismatch @ COUNT = %s:\n %s != %s\n",
count,
hex.EncodeToString(expectedCiphertext),
hex.EncodeToString(ciphertext)))
}
}
type cfbVerifier struct{}
func (o cfbVerifier) validate(count string, key, iv, plaintext, expectedCiphertext []byte) {
block, err := cast5.NewCipher(key)
if err != nil {
panic(err)
}
ciphertext := make([]byte, len(plaintext))
stream := cipher.NewCFBEncrypter(block, iv)
stream.XORKeyStream(ciphertext, plaintext)
if !bytes.Equal(ciphertext, expectedCiphertext) {
panic(fmt.Errorf("vector mismatch @ COUNT = %s:\n %s != %s\n",
count,
hex.EncodeToString(expectedCiphertext),
hex.EncodeToString(ciphertext)))
}
}
type ctrVerifier struct{}
func (o ctrVerifier) validate(count string, key, iv, plaintext, expectedCiphertext []byte) {
block, err := cast5.NewCipher(key)
if err != nil {
panic(err)
}
ciphertext := make([]byte, len(plaintext))
stream := cipher.NewCTR(block, iv)
stream.XORKeyStream(ciphertext, plaintext)
if !bytes.Equal(ciphertext, expectedCiphertext) {
panic(fmt.Errorf("vector mismatch @ COUNT = %s:\n %s != %s\n",
count,
hex.EncodeToString(expectedCiphertext),
hex.EncodeToString(ciphertext)))
}
}
func validateVectors(verifier vectorVerifier, filename string) {
vectors, err := os.Open(filename)
if err != nil {
panic(err)
}
defer vectors.Close()
var segments []string
var vector *vectorArgs
scanner := bufio.NewScanner(vectors)
for scanner.Scan() {
segments = strings.Split(scanner.Text(), " = ")
switch {
case strings.ToUpper(segments[0]) == "COUNT":
if vector != nil {
verifier.validate(vector.count,
unhexlify(vector.key),
unhexlify(vector.iv),
unhexlify(vector.plaintext),
unhexlify(vector.ciphertext))
}
vector = &vectorArgs{count: segments[1]}
case strings.ToUpper(segments[0]) == "IV":
vector.iv = segments[1][:16]
case strings.ToUpper(segments[0]) == "KEY":
vector.key = segments[1]
case strings.ToUpper(segments[0]) == "PLAINTEXT":
vector.plaintext = segments[1]
case strings.ToUpper(segments[0]) == "CIPHERTEXT":
vector.ciphertext = segments[1]
}
}
}
func main() {
validateVectors(ofbVerifier{},
"vectors/cryptography_vectors/ciphers/CAST5/cast5-ofb.txt")
fmt.Println("OFB OK.")
validateVectors(cfbVerifier{},
"vectors/cryptography_vectors/ciphers/CAST5/cast5-cfb.txt")
fmt.Println("CFB OK.")
validateVectors(cbcVerifier{},
"vectors/cryptography_vectors/ciphers/CAST5/cast5-cbc.txt")
fmt.Println("CBC OK.")
validateVectors(ctrVerifier{},
"vectors/cryptography_vectors/ciphers/CAST5/cast5-ctr.txt")
fmt.Println("CTR OK.")
}
Download link: verify_cast5.go