├── GraxCode's CrackMe Hard.jar ├── Java CrackMe 2.jar ├── README.md ├── noverify's crackme 3.jar ├── noverify's crackme 4.jar ├── noverify's crackme 5.jar ├── noverify's crackme 6.jar ├── noverify's crackme 7.jar └── solutions ├── crackme-1.md └── crackme-4.md /GraxCode's CrackMe Hard.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/GraxCode/java-crackmes/62573ea09fc7a3c1b401f062e2020c69e76d3c13/GraxCode's CrackMe Hard.jar -------------------------------------------------------------------------------- /Java CrackMe 2.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/GraxCode/java-crackmes/62573ea09fc7a3c1b401f062e2020c69e76d3c13/Java CrackMe 2.jar -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Java-CrackMes 2 | Welcome! This is a collection of java crackmes i made. 3 | 4 | | Crackme | Difficulty | Estimated time | Short description | Key format | Solution | 5 | | ------------- | ------------- | -------------- | -------------------- | ------------- | :------: | 6 | | #1 | ★★★☆☆ | 1 hour | Annoying obfuscation | 32-bit int | ✓ | 7 | | #2 | ★★★☆☆ | 1.5 hours | Annoying obfuscation | 32-bit int | ✗ | 8 | | #3 | ★★★★☆ | 6 hours | Dynamic invokation | 64-bit long | ✗ | 9 | | #4 | ★★☆☆☆ | 45 minutes | Easy but tricky | length 16 hex | ✓ | 10 | | #5 | ★★★★★ | 5 hours | Annoying subroutines | hex | ✗ | 11 | | #6 (*NEW*) | ★★★☆☆ | 2.5 hours | Lockpicking a door | alphanumeric | ✗ | 12 | | #7 (*NEW*) | ★☆☆☆☆ | 30 minutes | For beginners | hex | ✗ | 13 | 14 | Run each file with `java -jar .jar `, if that does not work, use `java -cp .jar `. 15 | The goal is to find a working key to input as argument, without bruteforcing the program, but with writing a keygen (that should not take longer than 30 seconds) or calculating the key by hand. Solutions with only the key are *not* accepted, you should explain how you solved it and attach the keygen you wrote (if you used one). Every crackme has been tested for a working key. There can be multiple solutions for some crackmes, but you do not have to find every solution. If you want to, you can submit solutions via issues, and I will add them to the repository. 16 | -------------------------------------------------------------------------------- /noverify's crackme 3.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/GraxCode/java-crackmes/62573ea09fc7a3c1b401f062e2020c69e76d3c13/noverify's crackme 3.jar -------------------------------------------------------------------------------- /noverify's crackme 4.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/GraxCode/java-crackmes/62573ea09fc7a3c1b401f062e2020c69e76d3c13/noverify's crackme 4.jar -------------------------------------------------------------------------------- /noverify's crackme 5.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/GraxCode/java-crackmes/62573ea09fc7a3c1b401f062e2020c69e76d3c13/noverify's crackme 5.jar -------------------------------------------------------------------------------- /noverify's crackme 6.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/GraxCode/java-crackmes/62573ea09fc7a3c1b401f062e2020c69e76d3c13/noverify's crackme 6.jar -------------------------------------------------------------------------------- /noverify's crackme 7.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/GraxCode/java-crackmes/62573ea09fc7a3c1b401f062e2020c69e76d3c13/noverify's crackme 7.jar -------------------------------------------------------------------------------- /solutions/crackme-1.md: -------------------------------------------------------------------------------- 1 | # Solution for CrackMe #1 2 |

3 |

Spoiler warning

4 | The way to solve this crackme is to overcome the obfuscation, and then interpret the bytecode correctly. 5 | A working key can be generated using this method: 6 | 7 | ```java 8 | int user_code_temp, user_code_crc, valid_code_crc; 9 | 10 | // a bit of optimization 11 | valid_code_crc = "XVCe".hashCode(); 12 | 13 | // outer, "permutation" loop 14 | for(int user_code = 1; user_code != 0; user_code++) { 15 | user_code_temp = user_code; 16 | user_code_crc = user_code_temp << 8; 17 | 18 | // inner, basic validation loop 19 | for(int j = 0; user_code_temp > 1; j++) { 20 | if ((-(user_code_temp%2)) == 0) { 21 | user_code_temp >>= 1; 22 | } else { 23 | user_code_temp = user_code_temp ^ 2; 24 | if (user_code_crc << 2 == 0) { 25 | // a bit more optimizations 26 | break; 27 | } 28 | user_code_temp--; 29 | } 30 | user_code_crc = (user_code_crc << user_code_temp) ^ (user_code_temp % 5); 31 | if ((user_code_crc << 2) == user_code_temp) { 32 | user_code_temp = user_code_temp ^ 6; 33 | } 34 | } 35 | 36 | // second stage validation 37 | // at this point, if this validation passes, we print the valid input value 38 | if (user_code_crc == valid_code_crc) { 39 | System.out.println(String.format("%d", user_code)); 40 | } 41 | } 42 | ``` 43 | 44 | The full explanation can be read at http://www.nullsecurity.org/article/crackmes_one_noverify_graxcode_java_crackme_1 45 | 46 | 47 |

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3 |

Spoiler warning

4 | 5 | There are two main methods. The real one is synthetic and hidden by some decompilers. 6 | The actual main method takes in a hex[16] and reverses it, and then calls the fake main method. 7 | Then it xors the value with `0xCAFEBABE` converted to BigInteger. Then it calls `AuthKey.valueOf` with the BigInteger converted to a decimal string. 8 | But the only possible number it takes to solve the crackme is `15542048963542891100`, which is hidden inside the `valueOf` method. 9 | With that information you can calculate the key easily. 10 | 11 |

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