Bash - Encode, Decode Base64 and Hex

Tools

xxd - make a hexdump or do the reverse. base64 - base64 encode/decode data and print to standard output

Encode hex

echo "hello" | xxd -p
68656c6c6f0a

Decode hex

echo "68656c6c6f0a" | xxd -r -p

Encode base64

echo "hello" | base64
aGVsbG8K

Decode base64

echo "aGVsbG8K" | base64 --decode

Encode/decode ROT13

echo "Hello" | tr '[A-Za-z]' '[N-ZA-Mn-za-m]'

Caesar cipher encoding

(from: https://gist.github.com/IQAndreas/030b8e91a8d9a407caa6) The Caesar Cipher shifts plaintext three letters to the left to create ciphertext.

In this case, tr '[A-Z]' '[X-ZA-W]', tr translates all occurrences of 'A' to 'X', 'B' to 'Y', 'C' to 'Z', 'D' to 'A', etc.

[X-ZA-W] just means that your output starts with the letter X and continues through the letter Z, then continues with the letter A through the letter W. You could also use [XYZABCDEFGHIJKLMNOPQRSTUVW] instead but tr understands the hyphen '-' to mean 'through'.

echo "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG" | tr '[A-Z]' '[X-ZA-W]'
QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD

Caesar cipher decoding

echo "QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD" | tr '[X-ZA-W]' '[A-Z]'
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG