Abstract: Examples relate to multiple microprocessor architecture for cold storage of digital currency. A hardware wallet may include a first microprocessor configured to establish a secure connection with a mobile device connected to a network having access to a blockchain and a second microprocessor configured to generate a private key and a public key for communication of transaction data onto the blockchain. The second microprocessor may initially use a hash function and the private key to encrypt the transaction data and produce a digital signature independent from the first microprocessor and subsequently provide the digital signature and the public key to the first microprocessor for communication onto the blockchain via the secure wireless connection with the mobile device. The second microprocessor may also encrypt and store the private key securely within the wallet's memory such that the private key is readable only by the second microprocessor.

Abstract: In a general aspect, a distributed ledger transaction is generated on a cold hardware wallet. Generating the distributed ledger transaction includes receiving, at the cold hardware wallet, ledger information from a network-connected device via a private module-to-device communication link. The ledger information may include account information for the distributed ledger transaction, and a timestamp identifying when the account information was received by the network-connected device from a public network. The cold hardware wallet may generate a message based on the account information, identify a private key stored in the cold hardware wallet, generate a digital signature based on the message and the private key, and generate the distributed ledger transaction based on the message and the digital signature. The cold hardware wallet may send the distributed ledger transaction to the network-connected device via the private module-to-device communication link for forwarding to the public network for settlement.

Abstract: In a general aspect, a distributed ledger transaction is generated on a cold hardware wallet. Generating the distributed ledger transaction includes receiving, at the cold hardware wallet, ledger information from a network-connected device via a private module-to-device communication link. The ledger information may include account information for the distributed ledger transaction, and a timestamp identifying when the account information was received by the network-connected device from a public network. The cold hardware wallet may generate a message based on the account information, identify a private key stored in the cold hardware wallet, generate a digital signature based on the message and the private key, and generate the distributed ledger transaction based on the message and the digital signature. The cold hardware wallet may send the distributed ledger transaction to the network-connected device via the private module-to-device communication link for forwarding to the public network for settlement.

Abstract: In a general aspect, secure messaging between electronic modules is described. In an example, a method includes: generating, by a first electronic module, a private key and a public key associated with the private key; communicating, by the first electronic module, an unencrypted message, including the public key, to a first network-connected device using a first module-to-device communication link; receiving, from the first network-connected device, an encrypted message including a symmetric encryption key generated by a second electronic module; decrypting, by the first electronic module, the encrypted message using the private key, wherein decrypting using the private key makes the symmetric encryption key available to the first electronic module; and establishing, by the first electronic module, a secure messaging channel with the second electronic module based on at least the symmetric encryption key.