Software Package Information Security

All Junos OS is delivered in signed packages that contain digital signatures, Secure Hash Algorithm (SHA-1), and Message Digest 5 (MD5) checksums. A package is installed only if the checksum within it matches the hash recorded in its corresponding file. Which checksum is used depends on the software version:

• Digital signatures are used when you upgrade or downgrade between Junos OS Release 7.0 and a later version.
• The SHA-1 checksum is used when you upgrade or downgrade between Junos OS Release 6.4 and a later version.
• The MD5 checksum is used when you upgrade or downgrade between Junos OS Release 6.3 or earlier and a later version.