Abstract: Tree-based key storage can be used to selectively grant access to an encrypted conversation history. For example, a system can access a ciphertext tree that includes an internal node with a set of child nodes. The internal node can correspond to a key and a ciphertext. The ciphertext can be generated by encrypting a set of child keys, corresponding to the set of child nodes, using the key. The set of child keys may have been used to encrypt messages associated with a conversation. The system can then provide the ciphertext to a client device. The client device can receive the key from a source, decrypt the ciphertext using the key to derive the set of child keys corresponding to the set of child nodes, and decrypt at least some of the encrypted messages using at least one key of the set of child keys.

Abstract: In one example, a participant device can receive a heartbeat message from a leader device associated with a videoconferencing meeting. The participant device can correspond to a participant in the videoconferencing meeting. The participant device can determine a current time, extract a send time from the heartbeat message, and determine an offset value indicating a difference between a first clock of the participant device and a second clock of the leader device. The participant device can then determine a last heartbeat message time based on the send time and the offset value. Based on the current time and the last heartbeat message, the participant device can determine whether to disconnect from or stay connected to the videoconferencing meeting.

Abstract: A liveness requirement can be enforced on a videoconference by performing some techniques described herein. For example, a system can sequentially generate strings during a videoconference. The system can sequentially transmit the strings to a host device associated with a host of the videoconference. The system can receive a communication from the host device during the videoconference. The system can determine whether the communication includes a most recently generated string among the strings. Based on determining that the communication excludes the most recently generated string, the system can discard the communication as outdated.

Abstract: Tree-based key storage can be used to selectively grant access to an encrypted conversation history. For example, a system can access a ciphertext tree that includes an internal node with a set of child nodes. The internal node can correspond to a key and a ciphertext. The ciphertext can be generated by encrypting a set of child keys, corresponding to the set of child nodes, using the key. The set of child keys may have been used to encrypt messages associated with a conversation. The system can then provide the ciphertext to a client device. The client device can receive the key from a source, decrypt the ciphertext using the key to derive the set of child keys corresponding to the set of child nodes, and decrypt at least some of the encrypted messages using at least one key of the set of child keys.

Abstract: In one example, a participant device can receive a heartbeat message from a leader device associated with a videoconferencing meeting. The participant device can correspond to a participant in the videoconferencing meeting. The participant device can determine a current time, extract a send time from the heartbeat message, and determine an offset value indicating a difference between a first clock of the participant device and a second clock of the leader device. The participant device can then determine a last heartbeat message time based on the send time and the offset value. Based on the current time and the last heartbeat message, the participant device can determine whether to disconnect from or stay connected to the videoconferencing meeting.

Abstract: Selective access to an encrypted conversation history can be granted as described herein. For example, a first client device can determine a message key used to encrypt messages associated with a conversation. The first client device can then generate a key ciphertext by: determining a prior secret key, determining a current secret key by hashing the prior secret key and the message key, and generating the key ciphertext by encrypting the prior secret key and the message key using the current secret key. The first client device can then transmit the key ciphertext to a server system. To grant the second client device with access to the encrypted messages, the first client device can transmit the current secret key to the second client device, which can obtain the key ciphertext from the server system and apply the current secret key to derive the message key and decrypt the messages.

Abstract: Selective access to an encrypted conversation history can be granted as described herein. For example, a first client device can determine a message key used to encrypt messages associated with a conversation. The first client device can then generate a key ciphertext by: determining a prior secret key, determining a current secret key by hashing the prior secret key and the message key, and generating the key ciphertext by encrypting the prior secret key and the message key using the current secret key. The first client device can then transmit the key ciphertext to a server system. To grant the second client device with access to the encrypted messages, the first client device can transmit the current secret key to the second client device, which can obtain the key ciphertext from the server system and apply the current secret key to derive the message key and decrypt the messages.

Abstract: Tree-based key storage can be used to selectively grant access to an encrypted conversation history. For example, a system can access a ciphertext tree that includes an internal node with a set of child nodes. The internal node can correspond to a key and a ciphertext. The ciphertext can be generated by encrypting a set of child keys, corresponding to the set of child nodes, using the key. The set of child keys may have been used to encrypt messages associated with a conversation. The system can then provide the ciphertext to a client device. The client device can receive the key from a source, decrypt the ciphertext using the key to derive the set of child keys corresponding to the set of child nodes, and decrypt at least some of the encrypted messages using at least one key of the set of child keys.

Abstract: A liveness requirement can be enforced on a videoconference by performing some techniques described herein. For example, a system can sequentially generate strings during a videoconference. The system can sequentially transmit the strings to a host device associated with a host of the videoconference. The system can receive a communication from the host device during the videoconference. The system can determine whether the communication includes a most recently generated string among the strings. Based on determining that the communication excludes the most recently generated string, the system can discard the communication as outdated.

Abstract: In one example, a participant device can receive a heartbeat message from a leader device associated with a videoconferencing meeting. The participant device can correspond to a participant in the videoconferencing meeting. The participant device can determine a current time, extract a send time from the heartbeat message, and determine an offset value indicating a difference between a first clock of the participant device and a second clock of the leader device. The participant device can then determine a last heartbeat message time based on the send time and the offset value. Based on the current time and the last heartbeat message, the participant device can determine whether to disconnect from or stay connected to the videoconferencing meeting.

Abstract: Selective access to an encrypted conversation history can be granted as described herein. For example, a first client device can determine a message key used to encrypt messages associated with a conversation. The first client device can then generate a key ciphertext by: determining a prior secret key, determining a current secret key by hashing the prior secret key and the message key, and generating the key ciphertext by encrypting the prior secret key and the message key using the current secret key. The first client device can then transmit the key ciphertext to a server system. To grant the second client device with access to the encrypted messages, the first client device can transmit the current secret key to the second client device, which can obtain the key ciphertext from the server system and apply the current secret key to derive the message key and decrypt the messages.

Abstract: Methods, computer readable media, devices, and systems provide for distributed machine learning. In one aspect, a method of training a model is disclosed. The method includes receiving, by a client device, from one or more servers, an intermediate model, training, by the client device, the intermediate model based on private data, and transmitting, by the client device, to the one or more servers, the trained intermediate model.

Abstract: Methods, computer readable media, devices, and systems provide for distributed machine learning. In one aspect, a method of training a model is disclosed. The method includes receiving, by a client device, from one or more servers, an intermediate model, training, by the client device, the intermediate model based on private data, and transmitting, by the client device, to the one or more servers, the trained intermediate model.

Abstract: Methods, computer readable media, devices, and systems provide for distributed machine learning. In one aspect, a method of training a model is disclosed. The method includes receiving, by a client device, from one or more servers, an intermediate model, training, by the client device, the intermediate model based on private data, and transmitting, by the client device, to the one or more servers, the trained intermediate model.