102 wallets type here for broader coverage of this
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[Type here] For broader coverage of this topic, see Cryptocurrency wallet. Bitcoin Core, a full client Electrum, a lightweight client A walletstores the information necessary to transact bitcoins. While wallets are often described as a place to holdor store bitcoins, due to the nature of the system, bitcoins are inseparable from the blockchain transaction ledger. A wallet is more correctly defined as something that "stores the digital credentials for your bitcoin holdings" and allows one to access (and spend) them.:ch. 1, glossaryBitcoin uses public-key cryptography, in which two cryptographic keys, one public and one private, are generated.At its most basic, a wallet is a collection of these keys. There are several modes which wallets can operate in. They have an inverse relationship with regards to trustlessness and computational requirements. Full clientsverify transactions directly by downloading a full copy of the blockchain (over 150 GB as of January 2018).They are the most secure and reliable way of using the network, as trust in external parties is not required. Full clients check the validity of mined blocks, preventing them from transacting on a chain that breaks or alters network rules.:ch. 1Because of its size and complexity, downloading and verifying the entire blockchain is not suitable for all computing devices. Lightweight clientsconsult full clients to send and receive transactions without requiring a local copy of the entire blockchain (see simplified payment verification–SPV). This makes lightweight clients much faster to set up and allows them to be used on low-power, low-bandwidth devices such as smartphones. When using a lightweight wallet, however, the user must trust the server to a certain degree, as it can report faulty values back to the user. Lightweight clients follow the longest blockchain and do not ensure it is valid, requiring trust in miners.Third-party internet services called online walletsoffer similar functionality but may be easier to use. In this case, credentials to access funds are stored with the online wallet provider rather than on the user's hardware.As a result, the user must have complete trust in the online wallet provider. A malicious provider or a breach in server security may cause entrusted bitcoins to be stolen. An example of such a security breach occurred with Mt. Gox in 2011.Physical wallets
[Type here] A paper wallet with a banknote-like design. Both the private key and the address are visible in text form and as 2D barcodes. A paper wallet with the address visible for adding or checking stored funds. The part of the page containing the private key is folded over and sealed. A brass token with a private key hidden beneath a tamper-evident security hologram. A part of the address is visible through a transparent part of the hologram.