add halfmd5 -m 5100 from PR #20

Merge pull request #20 from cyclone-github/dev

Author: cyclone-github

CHANGELOG.md

@@ -1,3 +1,8 @@
+### v1.2.2; 2026-01-23
+```
+added mode: halfmd5 (hashcat -m 5100)
+updated -help
+```
 ### v1.2.1; 2025-12-08
 ```
 added mode: morsedecode (Morse Code decoder)

README.md

@@ -9,15 +9,13 @@
 # hashgen - Cyclone's hash generator
 ```
 $ hashgen -m md5 -w rockyou.txt -b
-2025/08/23 19:18:27 Starting...
-2025/08/23 19:18:27 Processing file: rockyou.txt
-2025/08/23 19:18:27 Hash function: md5
-2025/08/23 19:18:27 CPU Threads: 16
-2025/08/23 19:18:28 Finished processing 14344391 lines in 0.465 sec (30.839 M lines/sec)
+2026/01/23 11:44:20 Starting...
+2026/01/23 11:44:20 Processing file: rockyou.txt
+2026/01/23 11:44:20 Hash function: md5
+2026/01/23 11:44:20 CPU Threads: 16
+2026/01/23 11:44:20 Finished processing 14344391 lines in 0.460 sec (31.215 M lines/sec)
 ```
-**As of the this writing, hashgen (go) has a 2,519% faster md5 hashrate vs the next fastest publicly available CPU based hash generator (see benchmarks).** While this is extremely fast, these hashrates can be beat by improved code optimization and/or coding in faster programming languages (I'm looking at you C, Rust and Zig).
-
-Since version `v2023-10-30.1600`, hashgen has a top recorded hasharate of 30,228,048 md5/sec on the test rig's Ryzen 7 3700X CPU! Much faster hashrates have been seen on higher end CPU's.
+**As of the this writing, hashgen (go) has a 2,519% faster md5 hashrate vs the next fastest publicly available CPU based hash generator (see benchmarks).** Since version `v2023-10-30.1600`, hashgen has a top recorded hasharate of 30,228,048 md5/sec on the test rig's Ryzen 7 3700X CPU! Much faster hashrates have been seen on higher end CPU's.
 
 Hashgen is a CLI hash generator written in Go and can be cross compiled for Linux, Raspberry Pi, Windows & Mac, although testing and compiling is mainly done on debian 12 linux.
 
@@ -77,6 +75,7 @@ To use hashgen, type your mode, wordlist input & hash output files with a simple
 | **`MDx`** | |
 | md4 | 900 |
 | md5 | 0 |
+| halfmd5 | 5100 |
 | md5passsalt | 10 |
 | md5saltpass | 20 |
 | md5md5 | 2600 |

hashgen.go

@@ -67,10 +67,13 @@ v1.2.0; 2025-11-08
 	updated yescrypt parameters to match debian 12 (libxcrypt) defaults
 v1.2.1; 2025-12-08
 	added mode: morsedecode (Morse Code decoder)
+v1.2.2; 2026-01-23
+	added mode: halfmd5 (hashcat -m 5100)
+	updated -help
 */
 
 func versionFunc() {
-	fmt.Fprintln(os.Stderr, "hashgen v1.2.1; 2025-12-08\nhttps://github.com/cyclone-github/hashgen")
+	fmt.Fprintln(os.Stderr, "hashgen v1.2.2; 2026-01-23\nhttps://github.com/cyclone-github/hashgen")
 }
 
 // help function
@@ -80,7 +83,7 @@ func helpFunc() {
 		"\n./hashgen -m md5 -w wordlist.txt -o output.txt\n" +
 		"./hashgen -m bcrypt -cost 8 -w wordlist.txt\n" +
 		"cat wordlist | ./hashgen -m md5 -hashplain\n" +
-		"\nAll Supported Options:\n-m {mode}\n-w {wordlist input}\n-t {cpu threads}\n-o {wordlist output}\n-b {benchmark mode}\n-cost {bcrypt, default=10}\n-hashplain {generates hash:plain pairs}\n" +
+		"\nAll Supported Options:\n-m {mode}\n-w {wordlist input}\n-t {cpu threads}\n-o {wordlist output}\n-b {benchmark mode}\n-cost {bcrypt, default=10}\n-hashplain {generates hash:plain pairs}\n-help {displays help}\n-version {displays version info}\n" +
 		"\nIf -w is not specified, defaults to stdin\n" +
 		"If -o is not specified, defaults to stdout\n" +
 		"If -t is not specified, defaults to max available CPU threads\n" +
@@ -104,12 +107,9 @@ func helpFunc() {
 		"crc64\n" +
 		"hex\t\t(encode to $HEX[])\n" +
 		"dehex/plaintext\t99999\t(decode $HEX[])\n" +
-		"keccak-224\t17700\n" +
-		"keccak-256\t17800\n" +
-		"keccak-384\t17900\n" +
-		"keccak-512\t18000\n" +
 		"md4\t\t900\n" +
 		"md5\t\t0\n" +
+		"halfmd5\t\t5100\n" +
 		"md5passsalt\t10\n" +
 		"md5saltpass\t20\n" +
 		"md5md5\t\t2600\n" +
@@ -144,6 +144,10 @@ func helpFunc() {
 		"sha3-256\t17400\n" +
 		"sha3-384\t17500\n" +
 		"sha3-512\t17600\n" +
+		"keccak-224\t17700\n" +
+		"keccak-256\t17800\n" +
+		"keccak-384\t17900\n" +
+		"keccak-512\t18000\n" +
 		"wpbcrypt\t(WordPress bcrypt-HMAC-SHA384)\n" +
 		"yescrypt\t(Linux shadow $y$)\n"
 	fmt.Fprintln(os.Stderr, str)
@@ -982,6 +986,11 @@ func hashBytes(hashFunc string, data []byte, cost int) string {
 		h := md5.Sum(data)
 		return hex.EncodeToString(h[:])
 
+	// halfmd5 -m 5100
+	case "halfmd5", "5100":
+		h := md5.Sum(data)
+		return hex.EncodeToString(h[:8])
+
 	// -m 10 md5(pass.salt), -m 20 md5(salt.pass)
 	case "10", "md5passsalt", "20", "md5saltpass":
 		salt, ok := makeSaltHex()