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Cryptography Details
=====================
Here is a high-level description of how this library works. Any discrepancy
between this documentation and the actual implementation will be considered
a security bug.
Let's start with the following definitions:
- HKDF-SHA256(*k*, *n*, *info*, *s*) is the key derivation function specified in
RFC 5869 (using the SHA256 hash function). The parameters are:
- *k*: The initial keying material.
- *n*: The number of output bytes.
- *info*: The info string.
- *s*: The salt.
- AES-256-CTR(*m*, *k*, *iv*) is AES-256 encryption in CTR mode. The parameters
are:
- *m*: An arbitrary-length (possibly zero-length) message.
- *k*: A 32-byte key.
- *iv*: A 16-byte initialization vector (nonce).
- PBKDF2-SHA256(*p*, *s*, *i*, *n*) is the password-based key derivation
function defined in RFC 2898 (using the SHA256 hash function). The parameters
are:
- *p*: The password string.
- *s*: The salt string.
- *i*: The iteration count.
- *n*: The output length in bytes.
- VERSION is the string `"\xDE\xF5\x02\x00"`.
- AUTHINFO is the string `"DefusePHP|V2|KeyForAuthentication"`.
- ENCRINFO is the string `"DefusePHP|V2|KeyForEncryption"`.
To encrypt a message *m* using a 32-byte key *k*, the following steps are taken:
1. Generate a random 32-byte string *salt*.
2. Derive the 32-byte authentication key *akey* = HKDF-SHA256(*k*, 32, AUTHINFO, *salt*).
3. Derive the 32-byte encryption key *ekey* = HKDF-SHA256(*k*, 32, ENCRINFO, *salt*).
4. Generate a random 16-byte initialization vector *iv*.
5. Compute *c* = AES-256-CTR(*m*, *ekey*, *iv*).
6. Combine *ctxt* = VERSION || *salt* || *iv* || *c*.
7. Compute *h* = HMAC-SHA256(*ctxt*, *akey*).
8. Output *ctxt* || *h*.
Decryption is roughly the reverse process (see the code for details, since the
security of the decryption routine is highly implementation-dependent).
For encryption using a password *p*, steps 1-3 above are replaced by:
1. Generate a random 32-byte string *salt*.
2. Compute *k* = PBKDF2-SHA256(SHA256(*p*), *salt*, 100000, 32).
3. Derive the 32-byte authentication key *akey* = HKDF-SHA256(*k*, 32, AUTHINFO, *salt*)
4. Derive the 32-byte encryption key *ekey* = HKDF-SHA256(*k*, 32, ENCRINFO, *salt*)
The remainder of the process is the same. Notice the reuse of the same *salt*
for PBKDF2-SHA256 and HKDF-SHA256. The prehashing of the password in step 2 is
done to prevent a [DoS attack using long
passwords](https://github.com/defuse/php-encryption/issues/230).
For `KeyProtectedByPassword`, the serialized key is encrypted according to the
password encryption defined above. However, the actual password used for
encryption is the SHA256 hash of the password the user provided. This is done in
order to provide domain separation between the message encryption in the user's
application and the internal key encryption done by this library. It fixes
a [key replacement chosen-protocol
attack](https://github.com/defuse/php-encryption/issues/240).
How it Works
Getting started with NFC Pay is simple and quick. Register your account, add your cards, and you're ready to make payments in no time. Whether you're paying at a store, sending money to a friend, or managing your merchant transactions, NFC Pay makes it easy and secure.
Download the NFC Pay app and sign up with your email or phone number. Complete the registration process by verifying your identity, and set up your secure PIN to protect your account.
Link your debit or credit cards to your NFC Pay wallet. Simply scan your card or enter the details manually, and you’re set to load funds, shop, and pay with ease.
To pay, simply tap your phone or scan the QR code at checkout. You can also transfer money to other users with a few taps. Enjoy fast, contactless payments with top-notch security.
Security System
NFC Pay prioritizes your security with advanced features that safeguard every transaction. From SMS or email verification to end-to-end encryption, we've implemented robust measures to ensure your data is always protected. Our security systems are designed to prevent unauthorized access and provide you with a safe and reliable payment experience.
Receive instant alerts for every transaction to keep track of your account activities.
Verify your identity through our Know Your Customer process to prevent fraud and enhance security.
Dramatically supply transparent backward deliverables before caward comp internal or "organic" sources.
All your data and transactions are encrypted, ensuring that your sensitive information remains private.
Monitor unusual activity patterns to detect and prevent suspicious behavior in real-time.
Why Choice Us
With NFC Pay, you get a trusted platform backed by proven expertise and a commitment to quality. We put our customers first, offering innovative solutions tailored to your needs, ensuring every transaction is secure, swift, and seamless.
Our team brings years of experience in the digital payments industry to provide reliable services.
We prioritize excellence, ensuring that every aspect of our platform meets the highest standards.
Your needs drive our solutions, and we are dedicated to delivering a superior user experience.
We continuously evolve, integrating the latest technologies to enhance your payment experience.
Testimonial Section
Hear from our users who trust NFC Pay for their everyday transactions. Our commitment to security, ease of use, and exceptional service shines through in their experiences. See why our clients choose NFC Pay for their payment needs and how it has transformed the way they manage their finances.
App Section
Unlock the full potential of NFC Pay by downloading our app, designed to bring secure, swift, and smart transactions to your fingertips. Whether you're paying at a store, transferring money to friends, or managing your business payments, the NFC Pay app makes it effortless. Available on both iOS and Android, it's your all-in-one solution for convenient and reliable digital payments. Download now and experience the future of payments!