Check a Change

Changed Message

A one-byte message change starts a new tag computation.

highlighted = computed this step

Change one message byte

The original message is 0x6869. The changed message is 0x686a.

message 0x6869→0x686a\text{message }0x6869\to 0x686a
Changed messageThe changed-message rows are recomputed from the same key and pads.Changed message - tag e7 changes to e8rowvaluecheckblock size2two-byte toy blockkey0f0epinned keyipad3636inner padinner key pad3938key xor ipadinner input39386869inner key pad || messageinner hash420x142 to 0x42opad5c5couter padouter key pad5352key xor opadouter input535242outer key pad || inner hashfinal tage70xe7 to 0xe7changed message686aone message byte changedchanged inner hash430x143 to 0x43changed final tage80xe8 to 0xe8old tag checkfaile7 != e8

The key and pads stay the same

The key remains 0x0f0e, and the inner key pad remains 0x3938.

inner pad=0x3938\text{inner pad}=0x3938
Changed messageThe changed-message rows are recomputed from the same key and pads.Changed message - tag e7 changes to e8rowvaluecheckblock size2two-byte toy blockkey0f0epinned keyipad3636inner padinner key pad3938key xor ipadinner input39386869inner key pad || messageinner hash420x142 to 0x42opad5c5couter padouter key pad5352key xor opadouter input535242outer key pad || inner hashfinal tage70xe7 to 0xe7changed message686aone message byte changedchanged inner hash430x143 to 0x43changed final tage80xe8 to 0xe8old tag checkfaile7 != e8

Only the message bytes change inside

The changed inner input is 0x3938686a.

changed inner input=0x3938686a\text{changed inner input}=0x3938686a
Changed messageThe changed-message rows are recomputed from the same key and pads.Changed message - tag e7 changes to e8rowvaluecheckblock size2two-byte toy blockkey0f0epinned keyipad3636inner padinner key pad3938key xor ipadinner input39386869inner key pad || messageinner hash420x142 to 0x42opad5c5couter padouter key pad5352key xor opadouter input535242outer key pad || inner hashfinal tage70xe7 to 0xe7changed message686aone message byte changedchanged inner hash430x143 to 0x43changed final tage80xe8 to 0xe8old tag checkfaile7 != e8

Summary

The changed message starts a new inner hash path.

changed message=0x686a\text{changed message}=0x686a
Changed messageThe changed-message rows are recomputed from the same key and pads.Changed message - tag e7 changes to e8rowvaluecheckblock size2two-byte toy blockkey0f0epinned keyipad3636inner padinner key pad3938key xor ipadinner input39386869inner key pad || messageinner hash420x142 to 0x42opad5c5couter padouter key pad5352key xor opadouter input535242outer key pad || inner hashfinal tage70xe7 to 0xe7changed message686aone message byte changedchanged inner hash430x143 to 0x43changed final tage80xe8 to 0xe8old tag checkfaile7 != e8