The HOTP Authenticator App is a demonstration project showcasing the integration of a Trusted Application (TA) developed using Java Card Technology into an Android mobile application. The Trusted Application is prototyped with the help of jCardSim, an open-source simulator for Java Card applications. This project supports the Licel Droidcon Hackathon, providing developers with a starting point to explore the development of secure and trusted mobile applications.
- HOTP Generation: Implements the HMAC-based One-Time Password (HOTP) algorithm as defined in RFC 4226.
- Java Card Simulation: The Trusted Application is developed and tested using jCardSim.
- Mobile Integration: The project demonstrates embedding the TA into an Android application for secure authentication workflows.
- jCardSim: Simulates the Java Card runtime environment for easy development and testing of Java Card applets.
- Trusted Application: A secure Java Card applet implementing HOTP logic.
- Android Application: Provides a user-friendly interface for scanning QR codes, managing secrets, and generating HOTP values.
- Android Studio: Required for building and running the mobile application.
- jCardSim Library: Included in the project dependencies.
| Field | Value | Definition |
|---|---|---|
| CLA | 00 | |
| INS | 02 | Import HMAC key |
| P1 | 00 | |
| P2 | 00 | |
| Lc | VAR | HMAC key bytes length |
| Data | HMAC key bytes | |
| Le | 01 |
Create a persistent instance of an HMAC key and return a unique ID. Implementation notes: HMAC keys must be stored in the HMACKey[] field, where the array index represents the unique key ID. The next key ID needs to be calculated as the index of the first empty (null) array element. If there are no null elements, a 6A84 error must be thrown.
| Field | Value | Definition |
|---|---|---|
| Data | HMAC key ID |
| SW1 | SW2 | Description |
|---|---|---|
| 90 | 00 | OK |
| 6D | 00 | Instruction no supported or invalid |
| 6A | 86 | Incorrect P1/P2 parameter |
| 6A | 84 | There is insufficient memory space to store new key |
| 67 | 00 | Wrong length |
| Field | Value | Description |
|---|---|---|
| CLA | 00 | |
| INS | 03 | Delete HMAC key |
| P1 | 00 | |
| P2 | VAR | HMAC Key ID |
| Lc | 00 | |
| Le | 00 |
Delete the persistent key and its metadata with the specified HMAC Key ID. Implementation notes: Before deletion, the HMAC Key value is erased by calling the clearKey method. The related array element must be set to null. If the index specified by HMAC Key ID is out of range or points to a null array element, a 6A83 error must be thrown.
| SW1 | SW2 | Description |
|---|---|---|
| 90 | 00 | OK |
| 6D | 00 | Instruction no supported or invalid |
| 6A | 86 | Incorrect P1/P2 parameter |
| 6A | 83 | HMAC Key with specified ID is not found |
| Field | Value | Description |
|---|---|---|
| CLA | 00 | |
| INS | 01 | Calculate HMAC |
| P1 | VAR | Algorithm type |
| P2 | VAR | HMAC Key ID (0..255) |
| Lc | 8 | Counter data length |
| Data | Counter data value | |
| Le | VAR | HMAC value |
Calculate HMAC value using specified HMAC Key and counter data
| Value | Description |
|---|---|
| 18 | ALG_HMAC_SHA1 |
| 19 | ALG_HMAC_SHA_256 |
| 1A | ALG_HMAC_SHA_384 |
| 1B | ALG_HMAC_SHA_512 |
| Field | Value | Description |
|---|---|---|
| Data | Calculated HMAC value |
| SW1 | SW2 | Description |
|---|---|---|
| 90 | 00 | OK |
| 6D | 00 | Instruction no supported or invalid |
| 6A | 86 | Incorrect P1/P2 parameter |
| 6A | 83 | HMAC Key with specified ID is not found |
| 67 | 00 | Wrong length |
| Field | Value | Description |
|---|---|---|
| CLA | 00 | |
| INS | 04 | Calculate HOTP value |
| P1 | VAR | Algorithm type |
| P2 | VAR | HMAC Key ID (0..255) |
| Lc | 8 | Counter data length |
| Data | Counter data value | |
| Le | VAR | HOTP value |
Calculate HOTP value using specified HMAC Key and counter data according to RFC 4226
| Value | Description |
|---|---|
| 18 | ALG_HMAC_SHA1 |
| 19 | ALG_HMAC_SHA_256 |
| 1A | ALG_HMAC_SHA_384 |
| 1B | ALG_HMAC_SHA_512 |
| Field | Value | Description |
|---|---|---|
| Data | Calculated HOTP value |
| SW1 | SW2 | Description |
|---|---|---|
| 90 | 00 | OK |
| 6D | 00 | Instruction no supported or invalid |
| 6A | 86 | Incorrect P1/P2 parameter |
| 6A | 83 | HMAC Key with specified ID is not found |
| 67 | 00 | Wrong length |