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authorrsiddharth <s@ricketyspace.net>2021-03-03 20:14:16 -0500
committerrsiddharth <s@ricketyspace.net>2021-03-03 20:14:16 -0500
commit51cce8132d7bd21f51613a1a78ea6652ffb222f4 (patch)
tree7c7683bb027aa34a1f7e1224808374afe592ac9e /challenge/c18.go
parente9f7ddf6c40844043d517931e157f5c53f8d36b4 (diff)
lib: add AESGenCTRFunc
Diffstat (limited to 'challenge/c18.go')
-rw-r--r--challenge/c18.go24
1 files changed, 1 insertions, 23 deletions
diff --git a/challenge/c18.go b/challenge/c18.go
index 00d1146..a84776e 100644
--- a/challenge/c18.go
+++ b/challenge/c18.go
@@ -11,31 +11,9 @@ import (
// Cryptopals #18 - Implement CTR, the stream cipher mode
func C18() {
- // Generates counter function for AES CTR mode.
- genCTRFunc := func(nonce uint64) func() []byte {
- ctr := uint64(0) // Counter
- ff := uint64(0xFF)
- cf := func() []byte {
- cb := make([]byte, 16) // counter block
- var i, j uint
- // Put nonce in the first 8 bytes in cb in little endian format
- for i = 0; i < 8; i++ {
- n := nonce & (ff << (i * 8)) // Reset all except the i^th byte of the nonce
- cb[i] = byte(n >> (i * 8)) // Retrieve i^th byte of the nonce
- }
- // Put counter in the next 8 bytes in cb in little endian format
- for i, j = 8, 0; i < 16; i, j = i+1, j+1 {
- n := ctr & (ff << (j * 8)) // Reset all except the j^th byte of the counter
- cb[i] = byte(n >> (j * 8)) // Retrieve j^th byte of the counter
- }
- ctr += 1 // Increment counter by 1
- return cb
- }
- return cf
- }
cipher := lib.Base64ToBytes("L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ==")
key := lib.StrToBytes("YELLOW SUBMARINE")
- ctrFunc := genCTRFunc(0)
+ ctrFunc := lib.AESGenCTRFunc(0)
plain, err := lib.AESDecryptCTR(cipher, key, ctrFunc)
if err != nil {
fmt.Printf("decryption failed: %v", err)