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Supporting crypto key change in message queuing systems

IP.com Disclosure Number: IPCOM000031017D
Original Publication Date: 2004-Sep-07
Included in the Prior Art Database: 2004-Sep-07
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Abstract

Proper maintenance of crypto keys is critical to the security of secured message. In order to achieve a high degree of security, crypto keys should be frequently changed. However, when symmetric cryptors are used, message receivers must be informed about which decryption keys should be used for individual messages in a secured manner. Currently, this can present some difficulties in practice. This article proposes a scheme that resolves such difficulties.

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Supporting crypto key change in message queuing systems

Disclosed is an algorithm for messaging systems that enables the identities of the crypto keys to be securely identified to allow a receiver to find the correct crypto key.

    The secrecy of encrypted data is dependent on the secure maintenance of crypto keys. It is a common practice that crypto keys are regularly changed in a security system in case they are compromised. This however can cause problems for a messaging system. In order to decrypt a message correctly, the decryption key must match the encryption used and this is true for both symmetric and non-symmetric cryptors. In reality, symmetric cryptors are more often used than non-symmetric ones for encrypting the entire message bodies as they are normally much more computation efficient.

    One way to allow key update to happen is to synchronise senders and receivers so that all messages already sent are decrypted by the receivers before a key is replaced. This is clearly not practical for a messaging system for messages may sit in a queue for a very long period before being received and it may be too expensive to perform regularly. In order to avoid synchronisation, receivers must, somehow, be told about the encryption key used for each individual message. In a PKI system, the encryption key (public key) can be sent to the receiver along with the message in clear text. This strategy, however, can not be applied to symmetric cryptor cases as decryption key is the same as the encryption key.

    Another approach is to send a key index number together the message. This scheme discloses the key identity and may suffer from index collision.

    This proposal suggests a very simple scheme for resolving this difficulty. All a sender needs to do is to send a key identity based on a secure one-way hashing of the symmetric enc...