The “public/private key method” is more commonly called public-key cryptography or asymmetric cryptography. It uses a related pair of keys: a public key that can be shared and a private key that must be kept secret. Depending on the algorithm, the pair can be used for encryption, digital signatures, or key agreement—but those operations are not interchangeable.
How public-key cryptography works
Unlike symmetric cryptography, which uses the same secret key for an operation such as encrypting and decrypting data, public-key cryptography uses two mathematically related keys. The public key is associated with an entity and may be shared; the private key is associated with that entity and is not made public. NIST describes the public key as derived from the private key, while deriving the private key from the public key is computationally infeasible in the scheme description it provides.
NIST’s glossary definition describes separate keys used to exchange data, with one key used to encrypt or digitally sign and the other used to decrypt or verify. Which key does what depends on the purpose and algorithm.
What the keys do in different operations
| Purpose | Key operation | What it provides |
|---|---|---|
| Encryption | A sender encrypts data or a key using the recipient’s public key; the recipient uses the corresponding private key to decrypt it. | Confidentiality: the intended recipient’s private key is needed to recover the protected material. |
| Digital signatures | The signer uses a private key to create a signature; others use the corresponding public key to verify it. | A way to check that a signature corresponds to the signer’s key and that the signed data has not changed. Verification is not decryption. |
| Key agreement | Participants use an algorithm-specific exchange to compute a shared secret. | A shared secret that can then be used in a secure communication scheme. |
NIST’s public-key glossary entry describes these uses. Not every public-key algorithm or key pair supports every operation. For example, NIST’s FIPS 186-5 specifies that an RSA digital-signature private key computes a signature and the corresponding public key verifies it.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
How public-key encryption protects information
- The recipient shares a public key. The recipient keeps the corresponding private key secret.
- The sender protects information for that recipient. The sender encrypts data—or often a key used to protect data—with the recipient’s public key.
- The recipient uses the private key. The corresponding private key enables decryption of the protected material.
This direction is for confidentiality: using the recipient’s public key lets others protect material for the recipient, while possession of the corresponding private key allows the recipient to recover it. It is different from signing, where the private key creates a signature and the public key checks it.
How a public key verifies a digital signature
A signer creates a digital signature with a private key. A verifier uses the corresponding public key to check the signature against the signed data. A successful verification supports confidence that the signature was produced using the matching private key and that the data matches what was signed; it does not mean the verifier has decrypted the data. NIST’s FIPS 186-5 gives RSA as a specific example of this signing and verification relationship.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Why a public key alone does not prove identity
A public key can be shared openly, but seeing a key does not by itself establish whose key it is. In real systems, a certificate or another trust mechanism can bind an identity to a public key. Without a way to establish that binding, a person could receive a key that belongs to someone else and mistake it for the intended party’s key. NIST’s glossary entry describes the public key’s association with an entity; the association still needs to be trusted in the context where the key is used.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why systems combine public-key and symmetric cryptography
Asymmetric algorithms are relatively slow and are not well suited to encrypting large messages directly. Practical systems therefore commonly use public-key techniques to protect or agree on a symmetric key, then use symmetric cryptography for bulk data. NIST’s introductory guide, SP 800-32, Introduction to Public Key Technology and the Federal PKI Infrastructure, discusses this role and characterizes asymmetric cryptography as a class of algorithms in which Alice has a private key and Bob and others have her public key.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesQuick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
