Cryptography

Cryptography is the science of protecting information by transforming it into an unreadable format, ensuring confidentiality, integrity, and authenticity. It uses algorithms and keys to encrypt and decrypt data, preventing unauthorized access.

Ciphers

Cipher Identifier & Analyzer

ROT13

# Alias
alias rot13="tr 'A-Za-z' 'N-ZA-Mn-za-m'"

# Encrypt
echo '<plaintext>' | tr 'A-Za-z' 'N-ZA-Mn-za-m'

# Decrypt
echo '<ciphertext>' | tr 'N-ZA-Mn-za-m' 'A-Za-z'

• Online ROT13 encoder

• Cyberchef's ROT13 Brute Forcer

ROT13.5

The ROT13.5 cipher is: ROT13 for letters and ROT5 for numbers.

# Encrypt
echo '<plaintext>' | tr 'A-Za-z0-9' 'N-ZA-Mn-za-m5-90-4'

# Decrypt
echo '<ciphertext>' | tr 'N-ZA-Mn-za-m5-90-4' 'A-Za-z0-9'

ROT47

# Encrypt
echo '<plaintext>' | tr '\!-~' 'P-~\!-O'

# Decrypt
echo '<ciphertext>' | tr 'P-~\!-O' '\!-~'

Caesar

# Encrypt
echo '<plaintext>' | tr '[a-zA-Z]' '[x-za-wX-ZA-W]'

# Decrypt
echo '<ciphertext>' | tr '[x-za-wX-ZA-W]' '[a-zA-Z]'

ROT Script

# ROT script
#!/usr/bin/bash
    
dual=abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz
phrase='<plaitext>'
rotat=13
newphrase=$(echo $phrase | tr "${dual:0:26}" "${dual:${rotat}:26}")
echo ${newphrase}

Vigenere

Use vigenere.sh -d to decrypt.

# Vigenere script
#!/usr/local/bin/bash

a="ABCDEFGHIJKLMNOPQRSTUVWXYZ"

[[ "${*/-d/}" != "" ]] &&
echo "Usage: $0 [-d]" && exit 1
m=${1:+-}

printf "string: ";read t
printf "keyphrase: ";read -s k
printf "\n"
for ((i=0;i<${#t};i++)); do
  p1=${a%%${t:$i:1}*}
  p2=${a%%${k:$((i%${#k})):1}*}
  d="${d}${a:$(((${#p1}${m:-+}${#p2})%${#a})):1}"
done
echo "$d"

Encoders

Encoding converts data into a different format using a specific scheme, primarily to ensure safe transmission or storage. Unlike encryption, encoding is reversible and not intended to keep data secret but to represent it in a compatible way.

Base64

# Encode
base64 <TEXT>

# Decode
base64 -d <TEXT>

URL

Urlencoder | Urldecoder

# Encode
echo "cat flag.txt" | jq -sRr @uri
hURL -U "cat flag.txt"

# Decode
echo "<urlEncodedString" | python3 -c 'import sys;from urllib.parse import unquote;print(unquote(sys.stdin.read()));'

Hex

# Encode
echo <text> | xxd -p

# Decode
echo <text> | xxd -p -r

Hashes

Hashes are fixed-size strings generated from data using mathematical functions. They uniquely represent the original input and are designed to be one-way, meaning the process is not reversible—it's practically impossible to retrieve the original data from the hash. This makes hashes useful for verifying data integrity and securely storing passwords, as even small changes in input produce completely different hashes.

MD5

md5sum <TEXT>
openssl md5 <TEXT>

SHA256

sha256sum <TEXT>
openssl sha256 <TEXT>

SHA1

sha1sum <TEXT>
openssl sha1 <TEXT>