challenge: do challenge 25

2 files changed, 236 insertions, 0 deletions

diff --git a/challenge/c25.go b/challenge/c25.go
new file mode 100644
index 0000000..6c698fc
--- /dev/null
+++ b/challenge/c25.go
@@ -0,0 +1,234 @@
+// Copyright © 2021 rsiddharth <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
+PEXODbk6a48oMbAY6DDZsuLbc0uR9cp9hQ0QQGATyyCESq2NSsvhx5zKlLtz
+dsnfK5ED5srKjK7Fz4Q38/ttd+stL/9WnDzlJvAo7WBsjI5YJc2gmAYayNfm
+CW2lhZE/ZLG0CBD2aPw0W417QYb4cAIOW92jYRiJ4PTsBBHDe8o4JwqaUac6
+rqdi833kbyAOV/Y2RMbN0oDb9Rq8uRHvbrqQJaJieaswEtMkgUt3P5Ttgeh7
+J+hE6TR0uHot8WzHyAKNbUWHoi/5zcRCUipvVOYLoBZXlNu4qnwoCZRSBgvC
+wTdz3Cbsp/P2wXB8tiz6l9rL2bLhBt13Qxyhhu0H0+JKj6soSeX5ZD1Rpilp
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+sCa2nQz/iEwyor6kPekLv1csm1Pa2LZmbA9Ujzz8zb/gFXtQqBAN4zA8/wt0
+VfoOsEZwcsaLOWUPtF/Ry3VhlKwXE7gGH/bbShAIKQqMqqUkEucZ3HPHAVp7
+ZCn3Ox6+c5QJ3Uv8V7L7SprofPFN6F+kfDM4zAc59do5twgDoClCbxxG0L19
+TBGHiYP3CygeY1HLMrX6KqypJfFJW5O9wNIF0qfOC2lWFgwayOwq41xdFSCW
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+5x9TzIAoW6ai13a8h/s9i5FlVRJDe2cetQhArrIVBquF0L0mUXMWNPFKkaQE
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+NhoIkUUS2R1oEV1toDj9iDzGVFwOvWyt4GzA9XdxT333JU/n8m+N6hs23MBc
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+4wkFCIhC/Y2ze/kNyis6FrXtStcjKC1w9Kg8O25VXB1Fmpu+4nzpbNdJ9LXa
+hF7wjOPXN6dixVKpzwTYjEFDSMaMhaTOTCaqJig97624wv79URbCgsyzwaC7
+YXRtbTstbFuEFBee3uW7B3xXw72mymM2BS2uPQ5NIwmacbhta8aCRQEGqIZ0
+78YrrOlZIjar3lbTCo5o6nbbDq9bvilirWG/SgWINuc3pWl5CscRcgQQNp7o
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+dVeaM24E/JtS8k9XAvgSoKCjyiqsawBMzScXCIRCk6nqX8ZaJU3rZ0LeOMTU
+w6MC4dC+aY9SrCvNQub19mBdtJUwOBOqGdfd5IoqQkaL6DfOkmpnsCs5PuLb
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+NjFnQb0/shnqTh4Mo/8oommbsBTUKPYS7/1oQCi12QABjJDt+LyUan+4iwvC
+i0k0IUIHvk21381vC0ixYDZxzY64+xx/RNID+iplgzq9PDZgjc8L7jMg+2+m
+rxPS56e71m5E2zufZ4d+nFjIg+dHD/ShNPzVpXizRVUERztLuak8Asah3/yv
+wOrH1mKEMMGC1/6qfvZUgFLJH5V0Ep0n2K/Fbs0VljENIN8cjkCKdG8aBnef
+EhITdV7CVjXcivQ6efkbOQCfkfcwWpaBFC8tD/zebXFE+JshW16D4EWXMnSm
+/9HcGwHvtlAj04rwrZ5tRvAgf1IR83kqqiTvqfENcj7ddCFwtNZrQK7EJhgB
+5Tr1tBFcb9InPRtS3KYteYHl3HWR9t8E2YGE8IGrS1sQibxaK/C0kKbqIrKp
+npwtoOLsZPNbPw6K2jpko9NeZAx7PYFmamR4D50KtzgELQcaEsi5aCztMg7f
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+zGMaKbTG4dns1OFB1g7NCiPb6s1lv0/lHFAF6HwoYV/FPSL/pirxyDSBb/FR
+RA3PIfmvGfMUGFVWlyS7+O73l5oIJHxuaJrR4EenzAu4Avpa5d+VuiYbM10a
+LaVegVPvFn4pCP4U/Nbbw4OTCFX2HKmWEiVBB0O3J9xwXWpxN1Vr5CDi75Fq
+NhxYCjgSJzWOUD34Y1dAfcj57VINmQVEWyc8Tch8vg9MnHGCOfOjRqp0VGyA
+S15AVD2QS1V6fhRimJSVyT6QuGb8tKRsl2N+a2Xze36vgMhw7XK7zh//jC2H`),
+		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
diff --git a/cryptopals.go b/cryptopals.go
index 742335d..ff359d8 100644
--- a/cryptopals.go
+++ b/cryptopals.go
@@ -67,5 +67,7 @@ func main() {
 		challenge.C23()
 	case 24:
 		challenge.C24()
+	case 25:
+		challenge.C25()
 	}
 }