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path: root/challenge/c25.go
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// Copyright © 2021 siddharth <s@ricketyspace.net>
// SPDX-License-Identifier: ISC

package challenge

import (
	"fmt"

	"ricketyspace.net/cryptopals/lib"
)

func C25() {
	//
	plain := lib.AESDecryptECB(
		lib.Base64ToBytes(`CRIwqt4+szDbqkNY+I0qbDe3LQz0wiw0SuxBQtAM5TDdMbjCMD/venUDW9BL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`),
		lib.StrToBytes("YELLOW SUBMARINE"))

	// Generate Nonce for AES counter function.
	nonce := uint64(lib.RandomInt(0, 10))

	// Generate random key.
	key, err := lib.RandomBytes(16)
	if err != nil {
		fmt.Printf("Error generating key %v", err)
		return
	}

	// Function for editing AES CTR cipher.
	editCipher := func(cipher, key []byte, offset int, newtxt []byte) []byte {
		if len(key) != 16 {
			return cipher // key must be 16 bytes.
		}
		if offset+len(newtxt) > len(cipher) {
			return cipher // Cannot edit.
		}

		// Get counter function.
		ctrFunc := lib.AESGenCTRFunc(nonce)

		// Get output block for the cipher.
		ob := make([]byte, 0)
		for {
			ob = append(ob, lib.AESCipher(ctrFunc(), key)...)
			if len(ob) >= len(cipher) {
				break
			}
		}

		// Make a copy of the cipher.
		cipherc := make([]byte, len(cipher))
		copy(cipherc, cipher)

		// Edit.
		c := lib.FixedXORBytes(newtxt, ob[offset:offset+len(newtxt)])
		for i, j := offset, 0; j < len(newtxt); i, j = i+1, j+1 {
			cipherc[i] = c[j]
		}
		return cipherc
	}

	// API Function for editing AES CTR cipher.
	apiEditCipher := func(cipher []byte, offset int, newtxt []byte) []byte {
		return editCipher(cipher, key, offset, newtxt)
	}

	// Cracks cipher using API function
	crack := func(cipher []byte) []byte {
		as := lib.FillBytes('A', len(cipher)) // 'A's.
		ec := apiEditCipher(cipher, 0, as)    // Edited cipher.

		// Get output block.
		ob := lib.FixedXORBytes(as, ec)

		// Crack cipher.
		p := lib.FixedXORBytes(cipher, ob)

		return p
	}

	// Get AES CTR cipher from plain text.
	cipher, err := lib.AESEncryptCTR(plain, key, lib.AESGenCTRFunc(nonce))
	if err != nil {
		fmt.Printf("Error encrypting plain: %v", err)
		return
	}

	// Crack plain text using API function.
	p := crack(cipher)
	fmt.Printf("%v", lib.BytesToStr(p))
}

// Output:
// I'm back and I'm ringin' the bell
// A rockin' on the mike while the fly girls yell
// In ecstasy in the back of me
// Well that's my DJ Deshay cuttin' all them Z's
// Hittin' hard and the girlies goin' crazy
// Vanilla's on the mike, man I'm not lazy.
//
// I'm lettin' my drug kick in
// It controls my mouth and I begin
// To just let it flow, let my concepts go
// My posse's to the side yellin', Go Vanilla Go!
//
// Smooth 'cause that's the way I will be
// And if you don't give a damn, then
// Why you starin' at me
// So get off 'cause I control the stage
// There's no dissin' allowed
// I'm in my own phase
// The girlies sa y they love me and that is ok
// And I can dance better than any kid n' play
//
// Stage 2 -- Yea the one ya' wanna listen to
// It's off my head so let the beat play through
// So I can funk it up and make it sound good
// 1-2-3 Yo -- Knock on some wood
// For good luck, I like my rhymes atrocious
// Supercalafragilisticexpialidocious
// I'm an effect and that you can bet
// I can take a fly girl and make her wet.
//
// I'm like Samson -- Samson to Delilah
// There's no denyin', You can try to hang
// But you'll keep tryin' to get my style
// Over and over, practice makes perfect
// But not if you're a loafer.
//
// You'll get nowhere, no place, no time, no girls
// Soon -- Oh my God, homebody, you probably eat
// Spaghetti with a spoon! Come on and say it!
//
// VIP. Vanilla Ice yep, yep, I'm comin' hard like a rhino
// Intoxicating so you stagger like a wino
// So punks stop trying and girl stop cryin'
// Vanilla Ice is sellin' and you people are buyin'
// 'Cause why the freaks are jockin' like Crazy Glue
// Movin' and groovin' trying to sing along
// All through the ghetto groovin' this here song
// Now you're amazed by the VIP posse.
//
// Steppin' so hard like a German Nazi
// Startled by the bases hittin' ground
// There's no trippin' on mine, I'm just gettin' down
// Sparkamatic, I'm hangin' tight like a fanatic
// You trapped me once and I thought that
// You might have it
// So step down and lend me your ear
// '89 in my time! You, '90 is my year.
//
// You're weakenin' fast, YO! and I can tell it
// Your body's gettin' hot, so, so I can smell it
// So don't be mad and don't be sad
// 'Cause the lyrics belong to ICE, You can call me Dad
// You're pitchin' a fit, so step back and endure
// Let the witch doctor, Ice, do the dance to cure
// So come up close and don't be square
// You wanna battle me -- Anytime, anywhere
//
// You thought that I was weak, Boy, you're dead wrong
// So come on, everybody and sing this song
//
// Say -- Play that funky music Say, go white boy, go white boy go
// play that funky music Go white boy, go white boy, go
// Lay down and boogie and play that funky music till you die.
//
// Play that funky music Come on, Come on, let me hear
// Play that funky music white boy you say it, say it
// Play that funky music A little louder now
// Play that funky music, white boy Come on, Come on, Come on
// Play that funky music