example code to blowfish encrypt/decrypt, using Go.

blowfish.go

package main

import (
  "crypto/cipher"
  "fmt"
  "go.crypto/blowfish"
)

func blowfishChecksizeAndPad(pt []byte) []byte {
  // calculate modulus of plaintext to blowfish's cipher block size
  // if result is not 0, then we need to pad
  modulus := len(pt) % blowfish.BlockSize
  if modulus != 0 {
    // how many bytes do we need to pad to make pt to be a multiple of blowfish's block size?
    padlen := blowfish.BlockSize - modulus
    // let's add the required padding
    for i := 0; i < padlen; i++ {
      // add the pad, one at a time
      pt = append(pt, 0)
    }
  }
  // return the whole-multiple-of-blowfish.BlockSize-sized plaintext to the calling function
  return pt
}

func blowfishDecrypt(et, key []byte) []byte {
  // create the cipher
  dcipher, err := blowfish.NewCipher(key)
  if err != nil {
    // fix this. its okay for this tester program, but...
    panic(err)
  }
  // make initialisation vector to be the first 8 bytes of ciphertext. 
  // see related note in blowfishEncrypt()
  div := et[:blowfish.BlockSize]
  // check last slice of encrypted text, if it's not a modulus of cipher block size, we're in trouble
  decrypted := et[blowfish.BlockSize:]
  if len(decrypted)%blowfish.BlockSize != 0 {
    panic("decrypted is not a multiple of blowfish.BlockSize")
  }
  // ok, we're good... create the decrypter
  dcbc := cipher.NewCBCDecrypter(dcipher, div)
  // decrypt!
  dcbc.CryptBlocks(decrypted, decrypted)
  return decrypted
}

func blowfishEncrypt(ppt, key []byte) []byte {
  // create the cipher
  ecipher, err := blowfish.NewCipher(key)
  if err != nil {
    // fix this. its okay for this tester program, but ....
    panic(err)
  }
  // make ciphertext big enough to store len(ppt)+blowfish.BlockSize
  ciphertext := make([]byte, blowfish.BlockSize+len(ppt))
  // make initialisation vector to be the first 8 bytes of ciphertext. you 
  // wouldn't do this normally/in real code, but this IS example code! :)
  eiv := ciphertext[:blowfish.BlockSize]
  // create the encrypter
  ecbc := cipher.NewCBCEncrypter(ecipher, eiv)
  // encrypt the blocks, because block cipher
  ecbc.CryptBlocks(ciphertext[blowfish.BlockSize:], ppt)
  // return ciphertext to calling function
  return ciphertext
}

func main() {
  var decryptedtext, encryptedtext, plaintext, paddedplaintext, secretkey []byte
  plaintext = []byte("this is the plaintext string")         // plaintext
  secretkey = []byte("1234567890abcdefghijklmnopqrstuvwxyz") // dat key
  // check the size of plaintext, does it need to be padded? because
  // blowfish is a block cipher, the plaintext needs to be padded to
  // a multiple of the blocksize. 
  paddedplaintext = blowfishChecksizeAndPad(plaintext)
  // lets encrypt
  encryptedtext = blowfishEncrypt(paddedplaintext, secretkey)
  // lets decrypt
  decryptedtext = blowfishDecrypt(encryptedtext, secretkey)
  // lets have a look-see
  fmt.Printf("      plaintext=%s\n", plaintext)
  fmt.Printf("  encryptedtext=%x\n", encryptedtext)
  fmt.Printf("  decryptedtext=%s\n", decryptedtext)
}