Make the Tag

Outer Tag

The outer hash turns the inner hash into the final toy tag.

highlighted = computed this step

The outer input uses the outer pad

The outer input joins 0x5352 with inner hash 0x42.

outer input=0x535242\text{outer input}=0x535242
Outer tagA toy HMAC-shaped table is recomputed from the pinned key and message.Outer tag - 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 outer input is exact bytes

The outer input is 0x535242.

outer input=0x535242\text{outer input}=0x535242
Outer tagA toy HMAC-shaped table is recomputed from the pinned key and message.Outer tag - 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 final toy tag is the outer hash

The outer byte sum is 0xe7, so the final toy tag is 0xe7.

H(0x535242)=0xe7H(0x535242)=0xe7
Outer tagA toy HMAC-shaped table is recomputed from the pinned key and message.Outer tag - 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 original message tag is 0xe7.

tag=0xe7\text{tag}=0xe7
Outer tagA toy HMAC-shaped table is recomputed from the pinned key and message.Outer tag - 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